Key Concept: Real-World Application, Advanced Reasoning

c) 200 cm$^2$

[Solution Description]

Let the width of the rectangle be $x$ cm. Then, the length is $2x$ cm. The perimeter of a rectangle is given by $2(length + width)$. So, $2(2x + x) = 60$. Simplifying, $2(3x) = 60$, which gives $6x = 60$. Solving for $x$, we get $x = 10$ cm. Therefore, the length is $2 * 10 = 20$ cm. The area of the rectangle is given by $length * width$, so $20 * 10 = 200$ cm$^2$.

Key Concept: Assertion-Reason

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description]

The assertion states that the gravitational force between two objects is always attractive, which is true according to Newton's law of gravitation. The reason provided is that gravitational force depends on the mass of the objects and the distance between them, which is also true. However, the reason does not directly explain why the force is always attractive; it merely describes the factors that influence the magnitude of the gravitational force. Therefore, while both the assertion and reason are true, the reason does not correctly explain the assertion.

Key Concept: Electroplating

b) Negative terminal

[Solution Description]

In electroplating, the metal to be deposited on another material is connected to the negative terminal of the battery. This is because the free metal ions are attracted to the negatively charged electrode and get deposited on it.

Key Concept: Conductivity, Electrical Safety

c) Wet floors make the body a better conductor of electricity

[Solution Description]

Water, especially when it contains mineral salts, is a good conductor of electricity. When standing on a wet floor, the water provides a path for the electric current to flow through the body to the ground, increasing the risk of electric shock.

Key Concept: Conductivity of Water

b) Wet hands decrease the resistance of the body

[Solution Description]

Wet hands contain small amounts of mineral salts that make water a good conductor of electricity. When you touch an electrical appliance with wet hands, the electric current can pass through your body, leading to an electric shock. This is because the human body becomes a path for the electric current to flow, which can cause severe harm or even death.

Key Concept: Conductivity, Electrical Safety

b) 0.22 A

[Solution Description]

To calculate the current passing through the person's body, we use Ohm's Law: $I = \frac{V}{R}$. Here, $V = 220$ V and $R = 1000$ $\Omega$. Substituting these values into the formula gives $I = \frac{220}{1000} = 0.22$ A.

Key Concept: Conductors and insulators, Chemical effects of electric current

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

Lemon juice is an acidic liquid that contains hydrogen ions ($H^+$) and citrate ions ($C_6H_5O_7^{3-}$). These ions are free to move within the liquid, allowing it to conduct electricity. When the ends of a tester are dipped into lemon juice, the circuit is completed due to the movement of these ions, and the bulb glows. Therefore, the assertion is true. The reason states that the presence of free-moving ions in a liquid allows it to conduct electricity, which is also true. Moreover, the reason correctly explains why the assertion is true because it is the free-moving ions in lemon juice that enable it to conduct electricity.

Key Concept: Tap water vs. Distilled water, Conductivity

b) Tap water contains impurities that conduct electricity

[Solution Description]

Tap water contains dissolved salts and minerals that dissociate into ions when dissolved. These ions are responsible for conducting electricity. On the other hand, distilled water is pure and lacks these ions, making it a poor conductor of electricity. The presence of impurities in tap water enables it to conduct electricity.

Key Concept: Conditions Affecting Conductivity

d) All of the above

[Solution Description]

Air is generally a poor conductor of electricity, but under certain conditions, such as during lightning, it can conduct electricity due to the ionization of air molecules.

Key Concept: Effect of Adding Salt

c) Conductivity increases

[Solution Description]

Distilled water is a poor conductor of electricity because it lacks ions. When common salt (NaCl) is added, it dissociates into Na$^+$ and Cl$^-$ ions, making the solution conductive.

Key Concept: Conduction of Electricity, Distilled Water, Salt Solution

c) Distilled water becomes a good conductor after adding salt

[Solution Description]

Distilled water is a poor conductor of electricity because it lacks ions. When a pinch of common salt (NaCl) is added, it dissociates into Na$^+$ and Cl$^-$ ions, which allow the solution to conduct electricity. Therefore, the conductivity increases after adding salt.

Key Concept: Conductivity of Solutions

d) Sugar in distilled water

[Solution Description]

Sugar does not dissociate into ions when dissolved in water, so a sugar solution does not conduct electricity. On the other hand, lemon juice (contains citric acid), caustic soda (a base), and salt solution all dissociate into ions, making them good conductors of electricity.

Key Concept: Conductivity of Solutions

d) Sugar solution

[Solution Description]

Sugar does not dissociate into ions when dissolved in water, so a sugar solution does not conduct electricity. Lemon juice, caustic soda solution, and potassium iodide solution all contain ions that allow them to conduct electricity.

Key Concept: Distilled Water

b) It becomes a good conductor

[Solution Description]

Distilled water is a poor conductor of electricity because it lacks salts. When common salt is dissolved in distilled water, it forms a salt solution, which becomes a good conductor of electricity.

Key Concept: Chemical Effects of Electric Current

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The assertion states that distilled water is a poor conductor of electricity, which is true because distilled water lacks dissolved salts or impurities that are necessary for conducting electricity. The reason provided is that distilled water does not contain any dissolved salts or impurities, which is also true and explains why distilled water is a poor conductor of electricity. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Key Concept: Testing solid materials for conductivity

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The assertion states that conductivity of a material can be tested using a simple circuit with a bulb. This is true because a conductive material will complete the circuit, allowing current to flow. The reason states that a bulb in the circuit will glow if the material conducts electricity. This is also true because the flow of current causes the bulb to glow. Furthermore, the reason correctly explains the assertion as the glowing of the bulb indicates the material\'s conductivity.

Key Concept: Basic Concept

d) Measuring electrical resistance

[Solution Description]

The primary method used to test the conductivity of a solid material is passing an electric current through it and measuring the resistance. This helps in determining how well the material conducts electricity.

Key Concept: Basic Concept

c) Number of free electrons

[Solution Description]

The electrical conductivity of a material is directly affected by the number of free electrons present in the material. More free electrons mean higher conductivity.

Key Concept: Effect of Adding Solutes

b) It becomes a good conductor

[Solution Description]

When a pinch of common salt is added to distilled water, the salt dissociates into sodium ($\text{Na}^+$) and chloride ($\text{Cl}^-$) ions. These free ions increase the ability of the water to conduct electricity, thus turning it from a poor conductor to a good conductor.

Key Concept: Chemical Effects of Electric Current

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The assertion states that distilled water does not conduct electricity. This is true because distilled water lacks ions, which are essential for conducting electricity. The reason states that distilled water is free of salts, which are necessary for the conduction of electricity. This is also true because salts dissolve into ions that allow the flow of electric current. The reason correctly explains the assertion, as the absence of salts in distilled water directly leads to its inability to conduct electricity.

Key Concept: Conduction of electricity in liquids, Tap water

b) Tap water contains dissolved salts that provide free ions for conduction.

[Solution Description]

Tap water contains dissolved salts and minerals, which dissociate into ions when dissolved in water. These free ions make tap water a good conductor of electricity. On the other hand, distilled water is pure and lacks these dissolved salts, making it a poor conductor of electricity. Hence, tap water conducts electricity more effectively than distilled water due to the presence of these ions.

Key Concept: Testing Electrical Conductivity

c) The current is too weak

[Solution Description]

Even if a liquid conducts electricity, the current may be too weak to heat the filament of the bulb sufficiently for it to glow. This can happen with liquids that are poor conductors but still allow some current to pass.

Key Concept: Effect of Impurities on Conductivity, Testing Methodology

b) The current is too weak to make the bulb glow

[Solution Description]

Adding common salt to distilled water introduces ions, making it a conductor of electricity. However, if the concentration of ions is too low, the current flowing through the circuit may be too weak to heat the filament of the bulb sufficiently, causing it not to glow. Alternatively, the bulb might be fused or the connections might be loose. Since the question specifies that the tester is functioning correctly, the most likely explanation is that the current is too weak due to the low concentration of ions in the solution.

Key Concept: Electrical Conductivity of Liquids

a) Lemon juice

[Solution Description]

Lemon juice contains ions that allow electric current to pass through it, making it a good conductor. Distilled water lacks ions and is a poor conductor. Tap water contains dissolved salts, making it a conductor. Vegetable oil does not conduct electricity as it lacks free ions.

Key Concept: Conductivity Testing

b) Vinegar

[Solution Description]

Lemon juice or vinegar are good conductors of electricity. When these liquids are placed between the two ends of the tester, they allow electric current to pass through, completing the circuit and making the bulb glow.

Key Concept: Conductivity of liquids

c) Vinegar is a good conductor of electricity

[Solution Description]

If the bulb glows when testing vinegar, it indicates that vinegar is conducting electricity. This means that the circuit of the tester is complete, allowing the electric current to flow through the vinegar and heat the filament of the bulb, causing it to glow.

Key Concept: Bulb-based tester functionality

d) All of the above

[Solution Description]

The bulb in the tester may not glow due to several reasons such as loose connections, a fused bulb, or used-up cells. Joining the free ends completes the circuit, but if any of these issues are present, the circuit will not function properly, and the bulb will not glow.

Key Concept: Good/Poor Conducting Liquids

d) Vegetable oil

[Solution Description] Vegetable oil is a poor conductor of electricity. When the free ends of the tester are dipped in vegetable oil, no significant electric current passes through the circuit. As a result, the magnetic field around the wire is too weak to cause any noticeable deflection in the compass needle.

Key Concept: Compass Needle Tester

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The assertion states that lemon juice causes deflection in the compass needle when tested with a compass needle tester. This is true because lemon juice contains free ions, which allow it to conduct electricity. When the free ends of the tester are dipped into lemon juice, the circuit is completed, and current flows through the wire wrapped around the compass needle, causing it to deflect.

The reason states that lemon juice is a good conductor of electricity due to the presence of free ions. This is also true because the presence of free ions in lemon juice enables it to conduct electricity efficiently, which is why it is classified as a good conductor.

Therefore, both the assertion and reason are true, and the reason correctly explains the assertion.

Key Concept: Good Conductors of Electricity

d) Lemon juice

[Solution Description]

From Table 11.1, we know that lemon juice is a good conductor of electricity and causes the compass needle to deflect. Other liquids like vegetable oil, milk, and honey are poor conductors and would not cause significant deflection. Therefore, lemon juice is the correct choice.

Key Concept: LED-based tester for weak currents

c) Vegetable oil

[Solution Description]

A compass needle deflects when an electric current flows through the wire wrapped around it. Liquids that do not conduct electricity will not allow current to flow, so there will be no deflection in the compass needle. Among the options, vegetable oil is a poor conductor of electricity and will not cause any deflection.

Key Concept: Conduction of liquids, LED tester, distilled water

b) The LED glows brightly

[Solution Description]

Distilled water is a poor conductor of electricity because it lacks free ions. When a pinch of common salt is added to the distilled water, it dissolves and dissociates into sodium and chloride ions. These free ions allow the water to conduct electricity, making it a good conductor. Therefore, after adding salt, the LED in the tester is likely to glow, indicating that the water now conducts electricity.

Key Concept: LED tester, weak currents, conduction of liquids

c) The liquid is a poor conductor of electricity

[Solution Description]

The LED in the tester glows when a weak current flows through it. If the LED does not glow, there are several possible reasons: the connections might be loose, the LED might be faulty, or the battery might be drained. Additionally, the liquid might not conduct electricity, or it might conduct so weakly that the current is insufficient to make the LED glow. Therefore, if the LED does not glow, one valid reason could be that the liquid is a poor conductor of electricity.

Key Concept: Conductivity of liquids, Mineral salts, Tap water

b) Tap water contains dissolved mineral salts that provide ions for conduction

[Solution Description]

Tap water contains small amounts of dissolved mineral salts, which dissociate into ions, making it a good conductor of electricity. Distilled water, on the other hand, is free of such salts and ions, making it a poor conductor.

Key Concept: Conductivity of Liquids

a) Lemon juice

[Solution Description]

From Table 11.1, we know that lemon juice is a good conductor of electricity, while vegetable oil and honey are poor conductors. Distilled water is also a poor conductor unless salts, acids, or bases are dissolved in it.

Key Concept: Conductivity of Liquids, Solutions of Acids, Bases, and Salts

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

Distilled water is a poor conductor of electricity because it is free of salts and other impurities that can dissociate into ions. When acids, bases, or salts are dissolved in distilled water, they dissociate into ions, making the solution a good conductor of electricity. Therefore, the Assertion is true as distilled water lacks free ions. The Reason is also true because solutions of acids, bases, and salts provide free ions that enable the conduction of electricity. Moreover, the Reason correctly explains the Assertion because it highlights the role of free ions in conductivity.

Key Concept: Effect of Salt on Conductivity

c) The bulb glows brightly

[Solution Description]

Distilled water is a poor conductor of electricity because it lacks ions. When common salt (sodium chloride) is dissolved in distilled water, it dissociates into sodium (Na$^+$) and chloride (Cl$^-$) ions. These ions make the solution conductive, allowing the bulb in the tester to glow.

Key Concept: Chemical Effects of Electric Current, Conductivity of Liquids

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

Lemon juice is indeed a good conductor of electricity as it contains citric acid, which dissociates into ions when dissolved in water. These ions are responsible for the conduction of electricity. The reason provided is also true because acids, in general, dissociate into ions in water, making the solution conductive. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

Key Concept: Conductivity of acids and bases, Real-world application

b) Caustic soda and potassium iodide

[Solution Description]

Solutions of acids, bases, and salts are good conductors of electricity due to the presence of ions. Among the given options, dilute hydrochloric acid (an acid) and caustic soda (a base) would produce highly ionized solutions, making them excellent conductors. Sugar and alcohol do not ionize significantly in water.

Key Concept: Chemical Effects of Electric Current

b) Chemical reactions occur

[Solution Description]

When an electric current passes through a conducting solution, it causes chemical reactions to occur. These reactions are known as the chemical effects of electric current. This phenomenon is commonly observed in processes like electrolysis.

Key Concept: Conductivity of Liquids

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

Distilled water is a poor conductor of electricity because it lacks dissolved salts or impurities that can carry electric charge. The absence of these ions prevents the flow of electric current through distilled water. Therefore, both the assertion and the reason are true, and the reason correctly explains why distilled water is a poor conductor.

Key Concept: Tap water, distilled water, conductivity

c) Tap water contains dissolved salts

[Solution Description]

Tap water contains dissolved salts and minerals, which dissociate into ions in water, making it a good conductor of electricity. Distilled water, however, is free of salts and minerals, so it lacks free ions and is a poor conductor of electricity.

Key Concept: Conductivity of Liquids, Distilled Water, Salt Solution

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The assertion states that distilled water is a poor conductor of electricity because it does not contain any dissolved salts or impurities. This is true as distilled water lacks free ions necessary for conductivity. The reason states that the presence of dissolved salts or impurities in water increases its conductivity by providing free ions. This is also true because dissolved salts dissociate into ions, which are charge carriers that enhance electrical conductivity. Moreover, the reason correctly explains the assertion since the absence of dissolved salts or impurities in distilled water directly leads to its poor conductivity.

Key Concept: Conductivity of Liquids

a) Lemon juice

[Solution Description]

From Table 11.1, we know that lemon juice is a good conductor of electricity because it causes the compass needle to show deflection. Vegetable oil and honey are poor conductors, and distilled water without any dissolved salts is also a poor conductor. Therefore, lemon juice is the correct answer.

Key Concept: Good Conductors, Poor Conductors, Tap Water

c) Tap water is a good conductor, while distilled water is a poor conductor.

[Solution Description]

Tap water contains dissolved salts and minerals, which dissociate into ions, allowing it to conduct electricity. This causes the compass needle to deflect. Distilled water, being free of salts and impurities, does not have free ions and hence does not conduct electricity, resulting in no deflection of the compass needle.

Key Concept: Poor Conductors: Distilled water

c) Because it is free of salts and impurities

[Solution Description]

Distilled water is free from salts and impurities, which are necessary for the conduction of electricity. Hence, it does not conduct electricity.

Key Concept: Classification of Liquids

c) Vegetable oil

[Solution Description]

From Table 11.1 and Activity 11.5, vegetable oil is a poor conductor of electricity as it does not contain free ions to conduct electricity. Milk and honey are also poor conductors, while lemon juice and vinegar are good conductors.

Key Concept: Conductivity of Liquids

a) Lemon juice

[Solution Description]

From Table 11.1, lemon juice is a good conductor of electricity as it causes the compass needle to deflect. Vinegar and salt solution are also good conductors, while distilled water is a poor conductor unless salts are added.

Key Concept: Conductivity of Distilled Water

b) It does not conduct electricity unless salts are added

[Solution Description]

Distilled water is free of salts and minerals, which makes it a poor conductor of electricity. However, when salts are dissolved in it, it becomes a good conductor.

Key Concept: Conductivity of Liquids

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description] Distilled water is free from impurities and dissolved salts, which means it does not contain ions that can carry electric charge. As a result, distilled water does not conduct electricity, making it a poor conductor of electricity. The absence of dissolved salts or ions in distilled water is the reason for its poor conductivity. Therefore, both the Assertion and Reason are true, and Reason correctly explains the Assertion.

Key Concept: Electrical Conductivity of Distilled Water

c) Distilled water is a poor conductor of electricity.

[Solution Description]

Distilled water is free of salts and impurities, making it a poor conductor of electricity. When tested with a tester, it does not show any deflection in the compass needle, indicating that it does not conduct electricity. However, when a pinch of common salt is dissolved in distilled water, it becomes a good conductor due to the formation of ions.

Key Concept: Chemical Reactions in Electrolysis

d) To protect the object from corrosion and improve its appearance

[Solution Description]

Electroplating is primarily used to deposit a thin layer of a desired metal on another material to enhance its properties. This process is widely used in industries to provide properties like corrosion resistance, improved appearance, and increased durability to the base material.

Key Concept: Disposal of Conducting Solution

c) The potential environmental pollution

[Solution Description]

The disposal of used conducting solutions in electroplating factories is a major concern because these solutions are often polluting waste. They may contain harmful chemicals that can damage the environment if not disposed of properly. Specific guidelines are in place to ensure that these solutions are disposed of in a way that minimizes environmental impact.

Key Concept: Chemical Effects of Electric Current, Electroplating

d) Assertion is false, but Reason is true.

[Solution Description]

The assertion states that electroplating is used to deposit a layer of chromium on iron because chromium is more reactive than iron. This is incorrect. Chromium is actually less reactive than iron, which is why it is used for plating. Chromium does not corrode easily and provides a shiny appearance, which are the main reasons for its use in electroplating. Therefore, the assertion is false.

The reason states that chromium plating protects iron from corrosion and provides a shiny appearance. This is true. Chromium is known for its anti-corrosive properties and shiny finish, making it ideal for protecting iron and enhancing its appearance.

Thus, the assertion is false, but the reason is true.

Key Concept: Electrolysis

b) Copper ions deposit on the negative electrode

[Solution Description]

When electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate ions. The copper ions are attracted to the electrode connected to the negative terminal of the battery, where they gain electrons and get deposited as copper atoms. Simultaneously, copper atoms from the other electrode dissolve into the solution to compensate for the loss of copper ions.

Key Concept: Chemical Effects of Electric Current

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description] When electric current is passed through a copper sulphate solution, the solution dissociates into copper ions ($\text{Cu}^{2+}$) and sulphate ions ($\text{SO}_4^{2-}$). The copper ions, being positively charged, are attracted to the electrode connected to the negative terminal of the battery. At this electrode, the copper ions gain electrons (reduction) and get deposited as copper atoms. This process is a direct result of the chemical effects of electric current. Therefore, both the Assertion and Reason are true, and the Reason correctly explains the Assertion.

Key Concept: Electrolysis of Copper Sulphate Solution

c) They gain electrons and get deposited on the cathode

[Solution Description]

When electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper ions ($\text{Cu}^{2+}$) and sulphate ions ($\text{SO}_4^{2-}$). The copper ions gain electrons at the electrode connected to the negative terminal of the battery and get deposited as copper atoms on the electrode. This process can be represented by the equation: $\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu}$. Therefore, the copper ions are reduced and deposited on the cathode.

Key Concept: Chemical Effects of Current, Electrodes

c) Positive terminal

[Solution Description]

The greenish-blue spot indicates a chemical reaction caused by the flow of electric current. According to Boojho's observation, the spot always appeared around the wire connected to the positive terminal of the battery. This suggests that the chemical effect was due to the positive terminal.

Key Concept: Conductivity of Liquids

c) Distilled water

[Solution Description]

Distilled water is a poor conductor of electricity because it lacks dissolved salts or minerals that can carry electric charge. On the other hand, tap water and lemon juice contain dissolved salts and acids, making them good conductors. Vegetable oil does not conduct electricity as it lacks ions.

Key Concept: Conduction of Electricity in Liquids

c) Distilled water

[Solution Description]

Distilled water is free of salts and minerals, making it a poor conductor of electricity. On the other hand, tap water, well water, and saltwater contain dissolved salts and minerals, which make them good conductors of electricity.

Key Concept: Electrolysis, Chemical Effects of Current

b) Bubbles of chlorine and hydrogen gases

[Solution Description]

When an electric current is passed through a saltwater solution, electrolysis occurs. At the anode (positive electrode), chlorine gas is produced due to the oxidation of chloride ions ($Cl^-$). At the cathode (negative electrode), hydrogen gas is produced due to the reduction of water molecules ($H_2O$). Therefore, bubbles of chlorine and hydrogen gases are observed at the respective electrodes.

Key Concept: Distilled Water and Conductivity

b) It lacks dissolved salts

[Solution Description]

Distilled water does not conduct electricity because it lacks dissolved salts and minerals, which are necessary for conductivity. When salts are added to distilled water, it becomes conductive. Therefore, the correct answer is that it lacks dissolved salts.

Key Concept: Chemical Effects of Electric Current, Conductivity of Liquids

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

Distilled water is a poor conductor of electricity because it does not contain any dissolved salts or impurities that can dissociate into free ions. For a solution to conduct electricity, it must have free ions that can move and carry electric charge. When salt is added to distilled water, it dissociates into Na$^+$ and Cl$^-$ ions, making the solution conductive. Therefore, both the Assertion and Reason are true, and the Reason correctly explains the Assertion.

Key Concept: Chemical Effects of Electric Current, Conducting Solutions

b) Saltwater

[Solution Description]

Pure distilled water does not conduct electricity because it lacks free ions. Saltwater contains dissolved salt ($NaCl$), which dissociates into $Na^+$ and $Cl^-$ ions, making it a good conductor. Sugar water does not dissociate into ions because sugar ($C_{12}H_{22}O_{11}$) is a non-electrolyte. Therefore, only the saltwater solution will cause the bulb to glow due to the presence of free ions.

Key Concept: Electrolysis of Water

b) Electrolysis

[Solution Description]

When electric current is passed through water, it dissociates into hydrogen and oxygen gases. This process is known as electrolysis of water.

Key Concept: Electrolysis of Water, Gas Formation

c) 6.72 L

[Solution Description]

First, calculate the moles of water decomposed:

$\text{Moles of } H_2O = \frac{3.6 \, \text{g}}{18 \, \text{g/mol}} = 0.2 \, \text{mol}$

From the balanced equation $2H_2O \rightarrow 2H_2 + O_2$, 2 moles of $H_2O$ produce 2 moles of $H_2$ and 1 mole of $O_2$. Therefore,

$\text{Moles of } H_2 = 0.2 \, \text{mol}, \quad \text{Moles of } O_2 = 0.1 \, \text{mol}$

Total moles of gas produced:

$\text{Total moles} = 0.2 + 0.1 = 0.3 \, \text{mol}$

Volume of gases at STP:

$\text{Volume} = 0.3 \, \text{mol} \times 22.4 \, \text{L/mol} = 6.72 \, \text{L}$

Key Concept: Purpose of Electroplating

c) To enhance their appearance and durability

[Solution Description]

Chromium is used for electroplating because it has a shiny appearance, does not corrode, and resists scratches. These properties make it ideal for applications where durability and appearance are important, such as car parts and bicycle handlebars. However, chromium is expensive, so it is more economical to coat a cheaper metal with chromium rather than making the entire object out of chromium.

Key Concept: Electroplating

c) Chromium

[Solution Description]

Chromium is commonly used for electroplating because it has a shiny appearance, does not corrode, and resists scratches. It is often plated on objects like car parts, bath taps, and bicycle handlebars to enhance their appearance and durability.

Key Concept: Electrolysis, Chemical effects, Metal deposition

c) Silver deposits on the cathode.

[Solution Description]

When silver nitrate (AgNO$_3$) solution is electrolyzed using silver electrodes, silver ions (Ag$^+$) are reduced at the cathode, depositing as solid silver. At the anode, silver oxidizes to form Ag$^+$ ions, which dissolve into the solution. The chemical effect is observed as the deposition of silver on the cathode and the dissolution of silver from the anode.

Key Concept: Electroplating

c) Zinc

[Solution Description]

Zinc is commonly used for electroplating iron to prevent rusting. This process is known as galvanization. The zinc coating acts as a sacrificial anode, which corrodes in place of the iron, thus protecting it from rust formation.

Key Concept: Chemical Effects of Electric Current, William Nicholson's Discovery

c) A deposit of copper metal

[Solution Description]

When an electric current is passed through a copper sulfate solution, the copper ions ($Cu^{2+}$) in the solution migrate towards the cathode. At the cathode, these ions gain electrons and get deposited as metallic copper. Therefore, a deposit of copper metal will be observed at the cathode.

Key Concept: Chemical Effects of Electric Current

b) Hydrogen gas is produced

[Solution Description]

During the electrolysis of water, hydrogen gas is produced at the electrode connected to the negative terminal of the battery. This is because water ($H_2O$) decomposes into hydrogen and oxygen gases when an electric current is passed through it.

Key Concept: Electrolysis of Water

b) Anode

[Solution Description]

During the electrolysis of water, oxygen gas is formed at the anode, which is connected to the positive terminal of the battery.

Key Concept: Electrolysis of Water

b) 32 g

[Solution Description]

First, calculate the number of moles of water. The molar mass of water ($H_2O$) is 18 g/mol. So, for 36 grams of water:

$\text{Number of moles} = \frac{36 \text{ g}}{18 \text{ g/mol}} = 2 \text{ mol}$

From the balanced chemical equation $2H_2O(l) \rightarrow 2H_2(g) + O_2(g)$, 2 moles of water produce 1 mole of oxygen gas. Therefore, 2 moles of water will produce 1 mole of oxygen gas.

The molar mass of oxygen gas ($O_2_) is 32 g/mol. Thus, the mass of oxygen gas produced is:

$\text{Mass of } O_2 = 1 \text{ mol} \times 32 \text{ g/mol} = 32 \text{ g}$

Key Concept: Electroplating, Chemical Effects of Electric Current

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

Electroplating is indeed used for enhancing the aesthetic appearance of objects, as mentioned in the assertion. This is one of its applications, particularly with metals like chromium, which are chosen for their shiny and scratch-resistant properties. The reason provided correctly explains why chromium is used for plating objects like car parts and bicycle handlebars. Both the assertion and the reason are true, and the reason is the correct explanation of the assertion.

Key Concept: Environmental Concern

c) Disposal of used conducting solutions

[Solution Description]

The disposal of used conducting solutions in electroplating factories is a major environmental concern because these solutions can be highly polluting and require specific disposal guidelines to protect the environment.

Key Concept: Electroplating, Application

c) To enhance the aesthetic appeal and durability

[Solution Description]

Chromium plating is commonly used in the manufacturing of car parts due to its desirable properties such as a shiny appearance, resistance to corrosion, and scratch resistance. Although chromium is expensive, it is economical to use it as a coating on cheaper metals rather than making the entire object out of chromium.

Key Concept: Definition of Electroplating

d) Electroplating

[Solution Description]

The process described in the question is known as electroplating. According to the syllabus, electroplating is defined as the process of depositing a layer of any desired metal on another material using electricity.

Key Concept: Electroplating, Environmental Impact

b) They contain heavy metals that are toxic to the environment.

[Solution Description] Used conducting solutions from electroplating factories often contain heavy metal ions such as copper, chromium, or nickel, which are toxic to the environment and living organisms. If not disposed of properly, these solutions can contaminate water bodies, soil, and groundwater, leading to severe environmental pollution. Therefore, specific disposal guidelines are followed to minimize their harmful impact.

Key Concept: Electroplating Process

b) Copper deposits on the negative electrode

[Solution Description]

When electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate ions. The copper ions migrate towards the electrode connected to the negative terminal of the battery and get deposited on it. Simultaneously, an equal amount of copper dissolves from the other electrode into the solution, maintaining the copper concentration in the solution.

Key Concept: Electroplating Process

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The Assertion states that electroplating is a process of depositing a layer of any desired metal on another material using electricity. This is true as electroplating involves the use of electric current to transfer metal ions from an electrode to a conductive surface. The Reason explains that electroplating is used to provide objects with properties like resistance to corrosion, shiny appearance, and protection from rust. This is also true as electroplating is widely used for these purposes in industries. Moreover, the Reason correctly explains why electroplating is performed, which aligns with the Assertion. Therefore, both the Assertion and Reason are true, and the Reason is the correct explanation of the Assertion.

Key Concept: Electroplating Waste Management

c) Pollution caused by improper disposal

[Solution Description]

In electroplating factories, the used conducting solution is a major environmental concern. This solution contains chemicals that can be harmful if not disposed of properly. Specific guidelines and regulations are in place to ensure that the waste is treated and disposed of in a way that minimizes environmental pollution. Proper disposal protects the environment from potential contamination by hazardous substances.

Key Concept: Electroplating, Carbon rod as electrode

c) Copper coating forms uniformly on the carbon rod

[Solution Description]

A carbon rod can act as a conductive electrode in the electroplating process. When connected to the negative terminal, copper ions from the solution will be reduced and deposited onto the surface of the carbon rod, forming a copper coating. This demonstrates that electroplating can occur on non-metallic conductive materials as long as they are capable of conducting electricity and providing a surface for deposition.

Key Concept: Electrode Replacement

c) Copper will coat the carbon rod

[Solution Description]

When a carbon rod is used instead of a copper plate connected to the negative terminal, a coating of copper will be obtained on the carbon rod.

Key Concept: Electroplating Mechanism

b) The deposited metal dissolves from the new cathode and deposits onto the new anode.

[Solution Description]

Interchanging the electrodes reverses the polarity of the circuit. The electrode originally connected to the positive terminal (anode) will now act as the cathode, and vice versa. This causes the deposited metal to dissolve from the new cathode and deposit onto the new anode, effectively reversing the electroplating process.

Key Concept: Electroplating, Chemical Effects of Electric Current

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The process of electroplating involves the deposition of a metal (copper in this case) on a cathode by passing an electric current through a solution containing the metal ions. The anode is made of the same metal that is to be deposited (copper here). When current is passed, copper atoms at the anode lose electrons and become copper ions in the solution. These copper ions migrate towards the cathode, where they gain electrons and are deposited as copper atoms. Thus, both the Assertion and Reason are true, and the Reason correctly explains the Assertion.

Key Concept: Electroplating

d) Assertion is false, but Reason is true.

[Solution Description]

The assertion states that during electroplating, metal ions always move towards the positive electrode, which is incorrect. In reality, metal ions move towards the negative electrode (cathode) during electroplating because they are positively charged and are attracted to the negative terminal of the battery. Therefore, the assertion is false. However, the reason correctly explains why metal ions move towards the negative electrode, which is true. Hence, the correct answer is that the assertion is false, but the reason is true.

Key Concept: Metal Ion Movement

c) They move towards the negative electrode

[Solution Description]

When electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper ions ($Cu^{2+}$) and sulphate ions ($SO_4^{2-}$). The copper ions move towards the electrode connected to the negative terminal of the battery, where they gain electrons and get deposited as metallic copper.

Key Concept: Electroplating Process

b) Positive electrode

[Solution Description]

In the electroplating process, the positive electrode (anode) is the one that loses metal. When electric current is passed through the solution, metal atoms from the anode dissolve into the solution to compensate for the metal ions being deposited on the cathode (negative electrode). This ensures that the concentration of metal ions in the solution remains constant.

Key Concept: Electroplating, Positive Electrode Dissolution

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

In the electroplating process, the anode (positive electrode) is made of the same metal that is to be deposited on the cathode (negative electrode). When an electric current is passed through the electrolyte solution, metal atoms from the anode dissolve into the solution as metal ions. These ions migrate towards the cathode and get deposited on it. This dissolution of the anode ensures that the concentration of metal ions in the solution remains constant, allowing the electroplating process to continue uninterrupted. Therefore, both the assertion and reason are true, and the reason correctly explains the assertion.

Key Concept: Electroplating Application

c) To prevent the food from reacting with iron

[Solution Description]

Tin is less reactive than iron, which prevents the food from coming into contact with iron and getting spoilt. This makes tin plating ideal for food cans.

Key Concept: Purpose of Chromium Plating

c) To enhance their appearance and durability

[Solution Description]

Chromium plating is done on objects like car parts and kitchen gas burners because chromium has a shiny appearance, does not corrode, and resists scratches. This enhances the durability and appearance of the objects.

Key Concept: Electroplating Process

d) Zinc

[Solution Description] Zinc is commonly used to coat iron to protect it from corrosion and rust formation through a process called electroplating.

Key Concept: Electroplating - Chromium Plating

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description] Chromium plating is indeed used on car parts to prevent rusting because chromium has properties that make it resistant to corrosion and scratching. The assertion is true as chromium plating provides a protective layer that prevents rusting on car parts. The reason is also true because chromium’s inherent properties include being non-corrosive and scratch-resistant. Moreover, the reason correctly explains why chromium is used for plating, as these properties are the primary reasons for its application in preventing rusting.

Key Concept: Electroplating

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The assertion states that electroplating is used to make jewelry affordable by coating less expensive metals with a thin layer of silver or gold. This is true because electroplating allows the creation of jewelry that has the appearance of precious metals like silver or gold but at a lower cost.

The reason states that the process of electroplating involves depositing a layer of desired metal on another material using electricity. This is also true as electroplating indeed uses electricity to deposit a thin layer of metal onto a substrate.

The reason correctly explains the assertion because it describes the process that makes it possible to create affordable jewelry through electroplating.

Key Concept: Assertion-Reason

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description] The assertion states that electroplating is used in the jewelry industry to make ornaments appear like gold or silver at a lower cost. This is true because electroplating allows less expensive metals to be coated with a thin layer of gold or silver, giving them the appearance of these precious metals without the high cost. The reason explains that electroplating involves depositing a thin layer of a desired metal on another material using electricity, which is also true and correctly explains how the process achieves the result described in the assertion. Therefore, both the assertion and reason are true, and the reason is the correct explanation of the assertion.

Key Concept: Chemical Effects of Electric Current, Electroplating Process

b) Copper ions are converted into copper atoms at the cathode.

[Solution Description]

When an electric current is passed through the copper sulphate solution, the copper sulphate dissociates into copper ions ($\text{Cu}^{2+}$) and sulphate ions ($\text{SO}_4^{2-}$). The copper ions are attracted to the electrode connected to the negative terminal of the battery (the cathode), where they gain electrons and get deposited as neutral copper atoms. Simultaneously, copper atoms from the anode (the electrode connected to the positive terminal) lose electrons and dissolve into the solution as copper ions, replenishing the copper in the solution.

Key Concept: Electroplating

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description] The assertion states that tin plating on iron cans prevents food contamination because tin is less reactive than iron. This is true since tin does not react easily with food, unlike iron, which can cause contamination. The reason states that tin acts as a barrier, preventing iron from coming into contact with food. This is also true because the tin layer covers the iron surface, ensuring that food does not come into direct contact with iron. Additionally, the reason correctly explains why tin plating prevents contamination by acting as a protective barrier. Therefore, both the assertion and the reason are true, and the reason is the correct explanation of the assertion.

Key Concept: Electroplating Definition

b) Electroplating

[Solution Description]

The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating. This is a standard and widely recognized definition in the field of chemistry and material science.

Key Concept: Application of Galvanization

c) Construction industry

[Solution Description]

Galvanization is widely used in industries such as construction, automotive, and pipeline industries to protect iron and steel structures from corrosion and rusting. Bridges, automobiles, and pipelines are common examples where galvanization is applied.