Tag: electrochemistry

Questions Related to electrochemistry

Examine the following statement sand select the correct option.
A : Electrolytic conduction is a physical change.
B : In Electrolytic conduction, positive as well as negative ions conduct electricity.

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Both A and B are true

  2. Both A and B are false

  3. A is true and B is false

  4. A is false but B is true

Show answer
Correct Option: D
Explanation:

Electrolytic conduction is a chemical change. It involves a redox reaction.
In electrolytic conduction, positive as well as negative ions conduct electricity.
For example, during electrolysis of molten NaCl, both $Na^+$ and $Cl^-$ ions are involved in the conduction of electricity.
Thus, A is false but B is true.

Assertion: In electrolysis of water, ions are not discharged at electrodes.
Reason: The current-carrying ions in an electrolytic cell are not necessarily discharged at the electrodes.
metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Both Assertion and Reason are true and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

  3. Assertion is true but Reason is false

  4. Assertion is false but Reason is true

  5. Both Assertion and Reason are false

Show answer
Correct Option: A
Explanation:

The current-carrying ions in an electrolytic cell are not necessarily discharged at the electrodes. This is true for the electrolysis of aqueous salt solutions in which water is involved in the electrode reactions and not the current carrying ions.
$2H _2O \rightarrow O _2 + 4H^+ +4e^-$    oxidation
$2H _2O + 2e^- \rightarrow H _2 +2OH^-$   reduction

Assertion: Electrolytic conductance increases with the increase of temperature
Reason: Metallic conductance decreases with the increase in temperature.

Choose the correct option.
metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Both Assertion and Reason are true and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

  3. Assertion is true but Reason is false

  4. Assertion is false but Reason is true

  5. Both Assertion and Reason are false

Show answer
Correct Option: B
Explanation:

The conductivity of an electrolyte depends on the temperature. With an increase in temperature, the conductivity of an electrolyte increases.This is due to increase in ionic mobility. 


For metals, the thermal conductivity is mainly a function of the motion of free electrons. As the temperature increases, the molecular vibrations increase (in turn increasing the mean free path of molecules). So, they obstruct the flow of free electrons, thus reducing the conductivity.

Which of the following will conduct electricity?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Ammonium acetate

  2. Ammonium hydroxide

  3. Sodium hydroxide

  4. formic acid

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Correct Option: A,C
Explanation:

Ammonium acetate is a salt. Salts conduct electricity due to complete dissociation. Ammonium hydroxide is a weak base and does not conduct electricity. Sodium hydroxide is a strong base and conducts electricity. Formic acid is a weak acid and does not conduct electricity. 

An electrolytic cell was set up. Dilute $HCl$ is placed in the cell and battery is switched on. The bulb is also connected through a battery. The bulb will:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. glow brightly

  2. not glow

  3. depends on amount of HCl

  4. none of the above

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Correct Option: A
Explanation:

$HCl$ is a strong acid and it has ions to carry the current. So the circuit will be completed and the bulb will glow brightly.

Which of the following is a poor conductor of electricity?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. $NH _4OH$

  2. $HCl$

  3. $CH _3COOH$

  4. $NaOH$

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Correct Option: A,C
Explanation:

Ammonium hydroxide and acetic acid are weak bases and acid respectively. Hence, they are poor conductors. 

In which of the following cases, conductivity decreases with an increase in temperature?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Fused $NaCl$

  2. $Cd$

  3. $NaOH$

  4. ${NH} _{4}OH$

Show answer
Correct Option: B
Explanation:

The electrical conductivity of a conductor will decrease with an increase in temperature. But for acids bases and salts raising the temperature gives more energy to the ions making them move faster, and hence increasing the conductivity.

Which does not show electrical conductance?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Sodium

  2. Diamond

  3. Potassium

  4. Graphite

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Correct Option: B,D
Explanation:

Sodium, potassium and Graphite all three are electrical conductor except Diamond which is an insulator of electric current.

Which of the following will conduct electricity?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. distilled water

  2. potable water

  3. well water

  4. none of the above

Show answer
Correct Option: C
Explanation:

Well water conducts electricity due to the presence of ions.

Which of the following solutions contains the greatest number of ions assuming that each solute is fully ionized?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. $1$ cm$^{-3}$ of $0.2M$ ${Na} _{2}{SO} _{4}$

  2. $1$ cm$^{-3}$ of $0.2M$ $Ca{Cl} _{2}$

  3. $1$ cm$^{-3}$ of $0.2M$ $NaCl$

  4. $1$ cm$^{-3}$ of $0.2M$ ${Cr} _{2}{({SO} _{4})} _{3}$

Show answer
Correct Option: D
Explanation:

No. of ions in 11 molecule of $Na _2SO _4=3$ 

No. of ions in 11 molecule of $CaCl _2=3$
No. of ions in 11 molecule of $NaCl=2$
No. of ions in 11 molecule of $Cr _2(SO _4) _3=5$
As the molarity and volume is same for all the given substances, number of ions will be greatest for the compound having greatest number of ions in one molecule. Therefore, $Cr _2(SO _4) _3$ will have the greatest number of ions.