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All questions of Electrolysis for EmSAT Achieve Exam

In the electrorefining of metals, impure metal is
  • a)
    cathode and oxidation taken place
  • b)
    anode and oxidation takes place
  • c)
    anode and reduction takes place
  • d)
    cathode and reduction takes place
Correct answer is option 'B'. Can you explain this answer?

Ameya Basu answered
Electrorefining of Metals:
In the electrorefining process, impure metal is purified through electrolysis.

Impure Metal as Anode:
- In electrorefining, the impure metal is attached to the anode.
- The anode undergoes oxidation, where the impurities present in the metal are oxidized and dissolve into the electrolyte.
- This leaves behind a more pure form of the metal at the cathode.
Therefore, the correct statement is:

Option B: Anode and oxidation takes place

A solution of copper(II) sulphate (VI) is electrolysed between copper electrodes by a currrent of 10.0 A for exactly 9650 s.Which remains unchanged?
  • a)
    Molar concentration of solution
  • b)
    Cathodic plate
  • c)
    Anodic plate
  • d)
    All of these
Correct answer is option 'A'. Can you explain this answer?

Ishani Patel answered

0.5 mole of copper is dissolved from the anode. Thus, its mass decreases. 0.5 mole of copper from the anode is deposited at the cathode. Thus, its mass increases.
Thus, molar concentration of aqueous solution of CuSO4 remains unchanged.

Select the correct observation about electrolysis.
  • a)
    Electric current is used to drive a non-spontaneous reaction
  • b)
    Ecell is positive and ΔG is negative
  • c)
    Cations and anions are discharged at the cathode and anode respectively
  • d)
    Overvoltage is responsible that a particular reaction takes place
Correct answer is option 'A,C,D'. Can you explain this answer?

Thus, electric current is used to carry out a non-spontaneous reaction.
Thus. (a) is correct.
(b) Since reactions are reverse of electrochemical cell, hence 
thus, (b) is incorrect
(c) cation goes to cathode and anion goes to anode and are discharged. Thus, correct
(d) some additional voltage called overvoltage is set up and thus other reactions also take place. thus correct

1 Faraday of electricity is passed through the solution containing 1 mole each of AgNO3, CuSO4, AlCland SiCl4. Elements are discharged at the cathode.Number of moles of Ag, Cu,Al and Si formed will be in the ratio of  
  • a)
    1 : 1 : 1 : 1
  • b)
    1 : 2 : 3 : 4
  • c)
    6 : 4 : 3 : 1
  • d)
    12 : 6 : 4 : 3
Correct answer is option 'D'. Can you explain this answer?

Aarya Khanna answered
Explanation:

To solve this problem, we need to determine the moles of each element formed at the cathode when 1 Faraday of electricity is passed through the solution containing 1 mole each of AgNO3, CuSO4, AlCl3, and SiCl4.

Step 1: Determine the number of moles of each compound

Given that there is 1 mole of each compound in the solution, the number of moles of AgNO3, CuSO4, AlCl3, and SiCl4 is 1 mole each.

Step 2: Calculate the number of moles of each element

We need to determine the moles of Ag, Cu, Al, and Si formed at the cathode.

Since AgNO3 contains 1 mole of Ag, CuSO4 contains 1 mole of Cu, AlCl3 contains 1 mole of Al, and SiCl4 contains 1 mole of Si, the number of moles of Ag, Cu, Al, and Si formed will be the same as the number of moles of the corresponding compounds.

Therefore, the ratio of moles of Ag, Cu, Al, and Si formed will be 1:1:1:1.

Step 3: Simplify the ratio

The given options are in different ratios, so we need to simplify the ratio of 1:1:1:1.

The simplified ratio of 1:1:1:1 is 12:6:4:3.

Therefore, the correct answer is option D) 12:6:4:3.

The metal that can not be obtained by electrolysis of an aqueous solution of its salt is
[JEE Main 2014]
  • a)
    Ag
  • b)
    Ca
  • c)
    Cu
  • d)
    Cr
Correct answer is option 'B'. Can you explain this answer?

Juhi Deshpande answered
Higher the position of element in the electrochemical series more difficult is the reduction of its cations.
If  (aq) is electrolysed, water is reduced in preference to it. Hence, it cannot be reduced electrolytically from their aqueous solution.

                                                  Passage I
A constant current of 30 A is passed through an aqueous solution of NaCl for a time of 1.00 h.
Thus Cl2 formed under STP condition is 
  • a)
    12.54 L
  • b)
    11.22 L
  • c)
    22.40 L
  • d)
    5.60 L
Correct answer is option 'A'. Can you explain this answer?

Ameya Basu answered
- **Given Data**
- Current (I) = 30 A
- Time (t) = 1.00 h
- Molar mass of Cl2 = 71 g/mol
- **Calculating the Amount of Charge Passed**
- Q = I * t
- Q = 30 A * 3600 s (1 hour = 3600 seconds)
- Q = 108000 C
- **Calculating the Moles of Cl2 Formed**
- 1 Faraday (F) of charge = 96500 C
- 1 mole of electrons = 2 moles of Cl2
- Moles of Cl2 = Q / (2F)
- Moles of Cl2 = 108000 C / (2 * 96500 C)
- Moles of Cl2 = 0.561 moles
- **Calculating the Volume of Cl2 at STP**
- Volume of 1 mole of gas at STP = 22.4 L
- Volume of Cl2 formed = Moles of Cl2 * 22.4 L
- Volume of Cl2 formed = 0.561 moles * 22.4 L
- Volume of Cl2 formed = 12.57 L
Therefore, the volume of Cl2 formed under STP conditions is approximately 12.57 L. Since the closest option is 12.54 L (option A), the correct answer is A.

Refining of impure metal is done by electrolysis using impure metal as anode.Select the correct statement about this refining.
  • a)
    E°cell of the net reaction is zero
  • b)
    metal to be refined is dissolved in the solution and deposited at the cathode.
  • c)
    Both (a) and (b)
  • d)
    None of the above
Correct answer is option 'C'. Can you explain this answer?

Mihir Joshi answered
Refining of impure metal is done by electrolysis using the impure metal as the anode. This process is known as electrorefining or electrolytic refining. It is commonly used to purify metals such as copper, zinc, and nickel.

Ecell of the net reaction is zero:

- The Ecell (cell potential) of the net reaction during the electrorefining process is not zero. In fact, it is a positive value. This means that the reaction is spontaneous and can proceed without the need for an external energy source. The positive Ecell indicates that the impure metal at the anode is oxidized and ions are being reduced at the cathode.

Metal to be refined is dissolved in the solution and deposited at the cathode:

- The metal to be refined is indeed dissolved in the electrolyte solution during the electrorefining process. When an electric current is passed through the electrolyte, metal cations from the impure metal at the anode are transferred into the electrolyte as metal ions. These metal ions then migrate towards the cathode, where they are reduced and deposited as pure metal. This deposition of pure metal at the cathode helps in the purification process.

Both (a) and (b):

- The correct statement about the refining of impure metal by electrolysis is that both statement (a) and (b) are correct. The Ecell of the net reaction is not zero, but a positive value indicating the spontaneity of the process. Additionally, the metal to be refined is dissolved in the electrolyte solution and deposited at the cathode, leading to the purification of the metal.

None of the above:

- This option is incorrect as both statement (a) and (b) are correct. The Ecell is not zero, and the metal is dissolved in the solution and deposited at the cathode during the electrorefining process.

In conclusion, the correct statement about the refining of impure metal by electrolysis is that both statement (a) and (b) are correct.

What product are formed during the electrolysis of a concentrated aqueous solution of sodium chloride using an electrolytic cell in which electrodes are separated by a porous pot?
I. Cl2(g)
II. NaOH(aq)
III. H2(g)
IV. NaClO(aq)
V. NaClO3(aq) 
Select the correct choice.  
  • a)
    I and  II
  • b)
    I , II and V
  • c)
    I , IiI and V
  • d)
    I , II and III
Correct answer is option 'D'. Can you explain this answer?

Cl2(g) is formed at anode and NaOH and H2 are formed at cathode. Since, cathode and anode are separated. Hence. there is no reaction between the products formed at the cathode and anode. 
Note: but these reaction do not occur
Note: NaCl is neutral pH = 7 initially. After electrolysis , NaOH is formed
Hence, solution become, basic pH >7

Which pair of electrolysis could be distinguished by the products of electrolysis using inert electrodes?
  • a)
    1 M CuSO4 ,1 M CuCl2
  • b)
    1 M KCl ,1 M KI
  • c)
    1 M AgNO,1 M CuSO4
  • d)
    1 M CuBr2 , 1 M NiBr2
Correct answer is option 'B,C'. Can you explain this answer?

Asha Nair answered
a(Cu So4 and CuCl2 changes to Cu and solution becomes colourless
(b) KCl changes to Cl2 (yellow)
KI changes to I2 (voilet)
Thus, distinguished.
(c) AgNo3 No change
CuSo4 (blue) changes to colourless
(d) CuBr2 (blue) both changes to colourles.
NiBr2 (Blue)

Comprehension Type
This section contains a passage describing theory, experiments, data, etc. Two questions related to the paragraph have been given. Each question has only one correct answer out of the given 4 options (a), (b), (c) and (d)
                                            Passage I
A constant current of 30 A is passed through an aqueous solution of NaCl for a time of 1.00 h.
Thus NaOH formed due to electrolysis is
  • a)
    40.2 g
  • b)
    44.8 g
  • c)
    31.1 g
  • d)
    22.4 g
Correct answer is option 'B'. Can you explain this answer?

Tanvi Bose answered
Electrolysis of NaCl Solution

  • A constant current of 30 A is passed through an aqueous solution of NaCl for 1 hour

  • NaCl undergoes electrolysis and produces NaOH and HCl

  • We need to calculate the amount of NaOH formed due to electrolysis



Calculation of NaOH formed

  • The formula for calculating the amount of NaOH formed is:

  • Amount of NaOH = (Current × Time × Atomic weight of Na × 1 mol of NaOH)/ (2 × Faraday's constant)

  • Plugging in the values, we get:

  • Amount of NaOH = (30 × 3600 × 23 × 1)/ (2 × 96500) = 44.8 g

  • Therefore, the correct answer is option 'B'



In summary, passing a constant current of 30 A through an aqueous solution of NaCl for 1 hour will result in the production of NaOH and HCl due to electrolysis. To calculate the amount of NaOH formed, we use the formula mentioned above and plug in the given values. The correct answer is option 'B', which is 44.8 g of NaOH formed.

What is the key role of hydrogen in the manufacturing process of margarine?
  • a)
    It acts as a preservative.
  • b)
    It provides a creamy texture.
  • c)
    It enhances the flavor.
  • d)
    It facilitates hydrogenation of oils.
Correct answer is option 'D'. Can you explain this answer?

Hydrogen plays a crucial role in the manufacturing of margarine by facilitating the hydrogenation of oils. This process involves adding hydrogen to unsaturated fats to convert them into saturated fats, resulting in a semi-solid consistency ideal for margarine production.

What is one of the main reasons for using electroplating with nickel?
  • a)
    To create a thicker layer of metal
  • b)
    To enhance the aesthetic appearance of objects
  • c)
    To increase the electrical resistance of objects
  • d)
    To reduce the weight of objects
Correct answer is option 'B'. Can you explain this answer?

One of the main reasons for using electroplating with nickel is to enhance the aesthetic appearance of objects. Nickel plating not only provides a shiny finish but also improves corrosion resistance, making it popular in jewelry and decorative items.

What ions are present in the electrolysis of acidified water?
  • a)
    Na+ and Cl-
  • b)
    Cu2+ and SO42-
  • c)
    K+ and I-
  • d)
    H+ and OH-
Correct answer is option 'D'. Can you explain this answer?

In the electrolysis of acidified water, the ions present include hydrogen ions (H+) and hydroxide ions (OH-). These ions play crucial roles during the electrolysis process, leading to the production of hydrogen and oxygen gases.

Which of the following is not an application of electrolysis?
  • a)
    Production of aluminum
  • b)
    Electroplating of jewelry
  • c)
    Electrolysis of water to produce hydrogen fuel
  • d)
    Production of plastics
Correct answer is option 'D'. Can you explain this answer?

The production of plastics is not an application of electrolysis. However, electrolysis is involved in the production of aluminum, electroplating of jewelry, and electrolysis of water for hydrogen fuel production.

Which of the following gases is produced at the anode during the electrolysis of brine?
  • a)
    Oxygen gas
  • b)
    Hydrogen gas
  • c)
    Chlorine gas
  • d)
    Carbon dioxide gas
Correct answer is option 'C'. Can you explain this answer?

Chlorine gas is produced at the anode during the electrolysis of brine (sodium chloride solution). Oxygen gas is produced at the anode during the electrolysis of water.

Which of the following metals can be extracted from their ores using electrolysis?
  • a)
    Copper
  • b)
    Silver
  • c)
    Iron
  • d)
    Aluminum
Correct answer is option 'D'. Can you explain this answer?

Aluminum can be extracted from its ore (bauxite) using electrolysis. Copper, silver, and iron are typically extracted using other methods.

What type of compounds can undergo electrolysis when an electric current flows through them?
  • a)
    Covalent compounds
  • b)
    Ionic compounds
  • c)
    Metallic compounds
  • d)
    Organic compounds
Correct answer is option 'B'. Can you explain this answer?

Ionic compounds are capable of undergoing electrolysis when an electric current passes through them. This is because ionic compounds can dissociate into ions in molten form or when dissolved in a solution, allowing the movement of ions to carry the electrical charge. This process leads to the decomposition of the compound into its constituent elements.

Where do negative ions, or anions, move within the electrolyte during electrolysis?
  • a)
    Cathode
  • b)
    Anode
  • c)
    Power source
  • d)
    Solution
Correct answer is option 'B'. Can you explain this answer?

Negative ions, or anions, within the electrolyte move towards the anode during electrolysis. At the anode, these anions release electrons as part of oxidation reactions. This movement of anions towards the anode is a key aspect of electrolysis, contributing to the overall flow of charge and the transformation of chemical species in the electrolyte. Understanding the behavior of anions is essential for comprehending the processes that occur during electrolysis.

What is the function of the cathode in an electrolytic cell?
  • a)
    Attract anions
  • b)
    Attract cations
  • c)
    Release electrons
  • d)
    Produce positively charged ions
Correct answer is option 'B'. Can you explain this answer?

The cathode in an electrolytic cell is the electrode that attracts positively charged ions (cations). When the cations reach the cathode, they can gain electrons and undergo reduction reactions, leading to the formation of new substances or the deposition of metals, depending on the specific electrolysis process.

Which of the following is an example of an electrolyte?
  • a)
    Pure water
  • b)
    Vinegar (acetic acid)
  • c)
    Cooking oil
  • d)
    Mercury
Correct answer is option 'B'. Can you explain this answer?

Vinegar (acetic acid) is an example of an electrolyte as it can conduct electricity when dissolved in water. Pure water, cooking oil, and mercury are not electrolytes.

What is the chemical formula for sodium chloride?
  • a)
    NaCl2
  • b)
    NaCl
  • c)
    Na2Cl
  • d)
    Na2Cl2
Correct answer is option 'B'. Can you explain this answer?

The chemical formula for sodium chloride is NaCl. It is composed of one sodium ion (Na+) and one chloride ion (Cl-).

What is the primary role of the strong electrolyte during electrolysis?
  • a)
    To facilitate the movement of ions
  • b)
    To decrease the conductivity of the solution
  • c)
    To provide a barrier to ion movement
  • d)
    To increase the temperature of the solution
Correct answer is option 'A'. Can you explain this answer?

The primary role of a strong electrolyte during electrolysis is to facilitate the movement of ions. Strong electrolytes dissociate fully into ions, which enhances the conductivity of the solution and allows for efficient electrochemical reactions to occur.

What is the process of electroplating used for?
  • a)
    To add a layer of metal onto an object
  • b)
    To purify metals
  • c)
    To create alloys
  • d)
    To increase the reactivity of metals
Correct answer is option 'A'. Can you explain this answer?

Electroplating is a process used to deposit a layer of metal onto an object. This technique is commonly employed to improve the appearance, corrosion resistance, and durability of the object being plated, making it a valuable method in many industrial applications.

Which of the following ions is preferentially discharged at the anode during the electrolysis of acidified water?
  • a)
    O2
  • b)
    OH-
  • c)
    SO42-
  • d)
    H+
Correct answer is option 'B'. Can you explain this answer?

During the electrolysis of acidified water, hydroxide ions (OH-) are preferentially discharged at the anode. They are oxidized to produce oxygen gas, while hydrogen ions (H+) are discharged at the cathode to produce hydrogen gas.

In the context of electrolysis, what is meant by the term "oxidizing agent"?
  • a)
    A substance that reduces other substances
  • b)
    A substance that does not participate in reactions
  • c)
    A substance that accepts electrons
  • d)
    A substance that donates electrons
Correct answer is option 'C'. Can you explain this answer?

An oxidizing agent is a substance that accepts electrons during a chemical reaction, leading to the oxidation of another substance. In electrolysis, the species being oxidized at the anode is often the one losing electrons to the oxidizing agent.

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