Question

A car battery produces electrical energy with the following chemical reaction. 

Pb + PbO2 + 2H2SO4 ; 2PbSO4 + 2H2O

What is the mole ratio of PbO2 to water?

Answer 1

1:2 is the answer to your question

Answer 2

Answer: the mole ratio of $PbO_2$ to water is 1:2

Explanation: According to the law of conservation of mass, the mass of the products must be same as the mass of the reactants in every chemical equation.Thus the number of atoms of every element must be same on both sides of the equation and we need to balance the chemical equation.

Here 1 mole of $PbO_2$  reacts with 1 mole of $Pb$ and 2 moles of $H_2SO_4$ to give 2 moles of $PbSO_4$ and 2 moles of $H_2O$. Thus the mole ratio of $PbO_2$ to $H_2O$ is 1:2