Electrochemistry Quiz - ICSE Class 12 Chemistry

Free practice quiz: Electrochemistry (ICSE Class 12 Chemistry). 26 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. For a spontaneous electrochemical reaction, which of the following conditions must be met?

   1. ΔG > 0 and E°cell < 0
   2. ΔG < 0 and E°cell > 0
   3. ΔG = 0 and E°cell = 0
   4. ΔG > 0 and E°cell > 0
   Show answer

   Answer: B. ΔG < 0 and E°cell > 0

   A spontaneous process is characterized by a negative Gibbs free energy change (ΔG < 0). The relationship between Gibbs free energy and cell potential is given by ΔG = -nFEcell. Therefore, for a spontaneous reaction (ΔG < 0), the cell potential (Ecell) must be positive (E°cell > 0).

2. The Nernst equation relates the cell potential to:

   1. Temperature and pressure only
   2. Concentration of reactants and products
   3. Gibbs free energy and entropy
   4. Electrode material and electrolyte concentration
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   Answer: B. Concentration of reactants and products

   The Nernst equation describes how the cell potential (Ecell) varies with the concentrations of the reacting species, temperature, and other thermodynamic parameters. Specifically, it relates Ecell to the standard cell potential (E°cell) and the reaction quotient (Q).

3. If the temperature of an electrochemical cell increases, how does the cell potential generally change?

   1. It increases if the reaction is exothermic.
   2. It decreases if the reaction is endothermic.
   3. It increases if ΔS is positive.
   4. It decreases if ΔS is negative.
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   Answer: C. It increases if ΔS is positive.

   The relationship between cell potential (E), Gibbs free energy (ΔG), entropy (ΔS), and temperature (T) is given by ΔG = ΔH - TΔS and ΔG = -nFE. Therefore, -nFE = ΔH - TΔS. So, E = -(ΔH/nF) + (TΔS/nF). If ΔS is positive, an increase in temperature (T) leads to a more positive value of the (TΔS/nF) term, thus increasing the cell potential (E).

4. Which metal can displace hydrogen from dilute acids?

   1. Cu
   2. Ag
   3. Au
   4. Zn
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   Answer: D. Zn

   A metal can displace hydrogen from dilute acids if it is more reactive than hydrogen. This means its standard electrode potential is more negative than that of the hydrogen electrode (0 V). Zinc (E° = -0.76 V) is above hydrogen in the electrochemical series and can displace hydrogen. Copper (E° = +0.34 V), Silver (E° = +0.80 V), and Gold (E° = +1.50 V) are below hydrogen and cannot displace hydrogen from dilute acids.

5. The relationship between standard electrode potential (E°) and the equilibrium constant (K) for a cell reaction is given by:

   1. E° = (RT/nF) ln K
   2. E° = -(RT/nF) ln K
   3. E° = (nF/RT) ln K
   4. E° = -(nF/RT) ln K
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   Answer: A. E° = (RT/nF) ln K

   The standard Gibbs free energy change (ΔG°) is related to the standard cell potential (E°) by ΔG° = -nFE°. It is also related to the equilibrium constant (K) by ΔG° = -RTlnK. Equating these two expressions gives -nFE° = -RTlnK, which rearranges to E° = (RT/nF)lnK.

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