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Electrolyte used in a lead-acid cell is
NaOH
only H2тАЛSO4тАЛ
only water
dilute H2тАЛSO4тАЛ
dilute H2тАЛSO4тАЛ
Quick Summary: The electrolyte used in a lead-acid battery is a solution of dilute sulfuric acid ($H_2SO_4$). It acts as the medium for ion transfer between the lead (Pb) anode and lead dioxide ($PbO_2$) cathode during charge and discharge cycles.
The electrolyte used in a lead-acid battery is a solution of dilute sulfuric acid (H2тАЛSO4тАЛ). It acts as the medium for ion transfer between the lead (Pb) anode and lead dioxide (PbO2тАЛ) cathode during charge and discharge cycles.
Pb+PbO2тАЛ+2H2тАЛSO4тАЛтЖТ2PbSO4тАЛ+2H2тАЛO тАФ Chemical reaction during discharge
During discharge, the sulfuric acid reacts with the plates to form lead sulfate (PbSO4тАЛ) and water, which reduces the concentration (specific gravity) of the electrolyte. During charging, the chemical reaction reverses, regenerating the sulfuric acid and restoring the concentration. The dilution with water is essential as concentrated sulfuric acid would be too viscous and could cause damage to the plates.
Specific gravity of fully charged electrolyte is typically between 1.250 and 1.280.
The electrolyte is composed of approximately 30-40% sulfuric acid and 60-70% distilled water.
A hydrometer is used to measure the state of charge by monitoring electrolyte density.
High surge current capability
Low internal resistance
Relatively low cost per watt-hour
Heavy and bulky due to lead plates
Sensitive to deep discharge and sulfation
Requires regular maintenance (topping up distilled water)
Automotive starting, lighting, and ignition (SLI) systems
Uninterruptible Power Supplies (UPS)
Standby power for telecommunication stations
Never use pure concentrated acid; it will destroy the plates and internal components.
Option B (only H2тАЛSO4тАЛ) is incorrect because pure acid lacks the necessary conductivity and fluidity, and Option C (only water) is non-conductive and lacks the sulfate ions needed for the reaction.
D is correct тАФ dilute H2тАЛSO4тАЛ is the standard electrolyte providing both the necessary conductivity and the sulfate ions for the electrochemical reaction.
Always remember that in lead-acid battery maintenance, add acid to water, never water to acid, to prevent exothermic splashing.