When an automotive battery is fully charged the sulfuric acid and water mixture will have specific gravity of about?
a. 2.5 b. 1.0 c. 0.15 d. 1.3

The correct answer is (d) 1.3

Specific gravity can be defined as the ratio of the substance density which has to be compared to the density of a standard usually it is water. If the specific density of water is 1 and the specific density of sulfuric acid is 1.835 which means that sulfuric acid is 1.835 times heavier than water. The electrolyte of a storage battery is a mixture of sulfuric acid and water.The specific gravity of sulfuric storage battery changes with amount of electrical charge.

Hence, by mixing both water and sulfuric acid the specific gravity of automotive battery is kept 1.3 at 80°F.