Question

Assertion:Lead storage battery is galvanic cell without salt bridge.
Reason:A secondary cell is a rechargeable cell.
(A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
(B) Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion.
(C) Assertion is correct but Reason is incorrect.
(D) Both Assertion and Reason are incorrect.

Answer 1

Hint: What kind of battery is present in an inverter or in automobiles? You must have observed while servicing, the technician adds some solution into the battery. Which is that solution and why is it added?

Complete answer:
-Lead storage battery is a galvanic cell which means it converts chemical energy into electrical energy.
-It is an example of secondary voltage cells which means that it can be recharged by reversing the direction of current flow and regenerating the original reactants. When a potential of slightly higher voltage than that generated by the cell is supplied to the electrodes present in the battery, the direction of current flow is reversed.
-Lead storage batteries are also called lead accumulators as they store electrical energy due to regeneration of original reactants.
-Cell can be represented as follows,
Pb(s)|$PbS{{O}_{4}}$|38%${{H}_{2}}S{{O}_{4}}(aq)$|$PbS{{O}_{4}}$(s)|$Pb{{O}_{2}}$(s)|Pb
-At anode (negatively charged electrode), lead plates packed with spongy lead are present and cathode (positively charged electrode), lead plates bearing lead dioxide are there. Both the electrodes are alternately arranged.
-The electrodes are immersed in an aqueous solution of 38% (by mass) ${{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}$ having density about 1.2g/ml.
- From the cell representation, we can understand that during discharge, at anode, spongy lead is oxidized to form $P{{b}^{2+}}$ which reacts with $SO_{4}^{2-}$ ions present in the electrolyte to form insoluble $PbS{{O}_{4}}$. The electrons released travel through the external circuit and re-enter the cathode and in the presence of protons present in the electrolyte, lead dioxide gets reduced to $P{{b}^{2+}}$ ions which again combine with $SO_{4}^{2-}$ ions present in the electrolyte to form insoluble $PbS{{O}_{4}}$.
-A salt bridge is used to separate two electrolyte solutions. But in lead storage batteries there is only one electrolyte. Thus, there is no need for a salt bridge.

Therefore, the answer is (B) Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion.

Note:
Lead storage battery is a secondary voltaic cell which acts as both galvanic at one point of time during discharge and as electrolytic cell at another point of time during recharge. Remember sulphuric acid is a strong electrolyte which is required to reverse the cell. Important application of lead storage batteries is inverters and automobile batteries.