Question

A Lead storage battery is the most important type of secondary cell having a lead anode and a

grid of lead packed with PbO2 as cathode. A 38% solution of sulphuric acid is used as

electrolyte. (Density=1.294 g mL-1

) The battery holds 3.5 L of the acid. During the discharge

of the battery, the density of H2SO4 falls to 1.139 g mL-1

. (20% H2SO4 by mass)

(1) Write the reaction taking place at the cathode when the battery is in use.

(2) How much electricity (in Coulombs) is required to carry out the reduction of one

mole of PbO2?

(3) What is the molarity of sulphuric acid before discharge?

(4) What is the mass of sulphuric acid in the solution after discharge?

(5) Write the products of electrolysis when dilute sulphuric acid is electrolysed using platinum electrodes..



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Answer 1

Answer:

We already know the formula for molarity=$\frac{moles}{volume(in L)}$

Moles of a substance=$\frac{given weight}{molecular mass}$

The density of H2SO4 is 1.294gm mL-1

Also, the molecular mass of H2SO4 is 98gm.

So, 1 mL of solution contains 1.294gm H2SO4

∴ 1L (1000mL) of solution contains 1294gm H2SO4

Also, the supplied solution contains 38% H2SO4.

molarity=$\frac{1294*38}{98*100}$

=5.018[M]

Answer 2

Explanation:

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