The simple form of the lead acid accumulator often has a negative pole of

Analysis

This question tests your knowledge of the chemical components of a secondary cell, specifically the lead-acid accumulator, which is commonly used in vehicles. You need to identify the material used for the negative electrode (anode) during the discharge process.

Concept Explanation

A lead-acid accumulator consists of two plates immersed in an electrolyte of dilute sulphuric acid ($H_2SO_4$):

1. Positive Plate (Cathode): Made of Lead (IV) oxide or Lead peroxide ($PbO_2$). This is usually brown in color.
2. Negative Plate (Anode): Made of spongy metallic lead ($Pb$). This is usually grey in color.

When the battery is in use (discharging), a chemical reaction occurs where the lead plate and the lead peroxide plate both react with the sulphuric acid to form lead (II) sulphate ($PbSO_4$).

Step-by-Step Solution

• Step 1: Identify the components of the lead-acid accumulator. The electrolyte is sulphuric acid.
• Step 2: Distinguish between the electrodes. The positive electrode is Lead peroxide ($PbO_2$).
• Step 3: Identify the negative electrode. The negative pole is composed of a porous or "spongy" lead plate.
• Step 4: Compare with the options provided. • A is incorrect (Zinc is used in Leclanché cells). • B is the positive pole (Lead peroxide). • C is the electrolyte, not an electrode. • D matches our identification of the negative pole.

Conclusion

The negative pole of a lead-acid accumulator is made of a lead plate.

Exam Tip: To remember this easily, think of the "P" in Positive and Peroxide. The positive plate is Lead Peroxide. Since the negative plate is the other one, it must be the plain Lead plate.