Answer :

pyromorphite
CH4 + 2O2 ----> CO2 + 2H2O

according to the reaction:
1 mole of CH4 ----------- 2 moles of H2O
12,5 moles of CH4 ----------- x
x = 25 moles of H2O

Answer: 25 moles of water are produced.

Explanation:

Combustion is a type of chemical reaction in which fuel is reacted with oxygen to form carbon dioxide and water.

Example:  

[tex]CH_4+2O_2 \rightarrow CO_2+2H_2O[/tex]

According to stoichiometry:

1 mole of methane on combustion produces= 2 moles of water

12.5 moles of methane on combustion produces= [tex]\frac{2}{1}\times 12.5=25[/tex] moles of water

Thus 25 moles of water are produced from the combustion of 12.5 moles of methane.