ELECTROCHEMISTRY QUIZ-7

Q1. How many atoms of calcium will be deposited from a solution of CaCl_2 by a current 0.25 mA flowing for 60 s?

•  0.46 ×〖10〗^18
•  1.24 ×〖10〗^18
•  2.34 ×〖10〗^18
•  4.68 ×〖10〗^18

Solution

Q2.Which is correct about fuel cells?

•  These are used to provide power and drinking water to astronauts in space programme
•  All of the above
•  These are more efficient and free from pollution
•  Cells continuously run as long as fuels are supplied

Solution
These are characteristics of fuel cells

Q3.  Aluminium oxide may be electrolysed at 1000℃ to furnish aluminium metal (atomic mass = 27 u; 1 F = 96500 C). The cathode reaction is Al^(3+)+〖3e〗^-⟶Al^0 To prepare 5.12 kg of aluminium metal by this method would require

•   5.49 × 〖10〗^1 C of electricity
•  5.49 × 〖10〗^4 C of electricity
•  1.83 × 〖10〗^7 C of electricity
•  5.49 × 〖10〗^7 C of electricity

Solution

Q4. In a galvanic cell, which is wrong?

•  Anode has negative polarity
•  Cathode has positive polarity
•  Reduction takes place at cathode
•  Reduction takes place at anode

Solution
Reduction is always carried out at cathode

Q5.Which of the following will form a cell with the highest voltage?

•  2 M Ag^+,0.1 M Co^(2+)
•  1 M Ag^+,1 M Co^(2+)
•  2 M Ag^+,2 M Co^(2+)
•  0.1 M Ag^+,2 M Co^(2+)

Solution
 

Q6. The oxidation potential of Mg and Al are + 2.37 and + 1.66 volt respectively. The Mg in chemical reactions :

•  Will be replaced by Al
•  Will replace Al
• Will not be able to replace Al
•  None of the above

Solution
Metal having higher E_OP^° replaces the other from its solution

Q7.The conductivity of strong electrolyte

•  Depends upon density of electrolyte itself
•  Does not change with dilution
•  Increases on dilution slightly
•  Decreases on dilution

Solution
C

Q8.If ϕ denotes standard reduction potential, which is true:

•  E_cell^°= ϕ_L+ ϕ_R
•  E_cell^°= ϕ_R- ϕ_L
•  E_cell^°= ϕ_L- ϕ_R
•  E_cell^°=(ϕ_L+ ϕ_R)

Solution

Q9.The standard electrode potential of hydrogen electrode at 1 M concentration and hydrogen gas at 1atm pressure is

•  1 V
•  6 V
•  8 V
•  0 V

Solution
D

Q10. According to Kohlrausch’s law the limiting value of equivalent conductivity of an electrolyte A_2 B is given by :

•  2λ_(A^+)^∞ + λ_(B^(-2))^∞
•  λ_(A^+)^∞ +1/2 λ_(B^(-2))^∞
•  1/2 λ_(A^+)^∞ + λ_(B^(-2))^∞
• λ_(A^+)^∞ + λ_(B^(-2))^∞

Solution
This is Kohlrausch law for a_2 b type of electrolytes