Over a period of time, the concentration of sulfuric acid in a lead storage battery of an automobile has decreased from 38 percent by mass(density=1.29 g/mL) to 26 percent by mass(1.19 g/mL). Assume the volume of the acid remains constant at 715 mL. a)Calculate the total charge in coulombs supplied by the battery.

Question

b)How long in hours will it take to recharge the battery back to the original sulfuric acid using a current of 24.2 A?

Answer 1

I would do this.
Calculate M of each of the solutions.
1.29 g/mL x 1000 mL x 0.38 x (1/98) = ?M
1.19 g/mL x 1000 mL x 0.26 x (1/98) = ?M
Convert each to mols in the 715 mL.
for the 1.29 it is ?M x 0.715 = ?
for the 1.19 is is ?M x 0.715 = ?

Now if you subtract the two mols you will have the mols H2SO4 used by the battery and that times 98 = grams H2SO4 used = ? grams H2SO4.
You know that 96,485 coulombs are used for every 49 grams (98g H2SO4/2e change).
96,485 coulombs x ?g H2SO4/49g) = ?C

For part 2,
C = amperes x seconds.
Plug in the numbers and solve for seconds. Convert seconds to hours.