Question

CH4 + 2O2 = CO2+2H2O

If 312g of CO2 is produced what mass of CH4 is required?

Answer 1

$CH_4+2O_2 \rightarrow CO_2+2H_2O$

Weight of $CO_2$ given $=$ 312 gm

moles of $CO_2$ $(n_{CO_2})=$ $\dfrac{weight of CO_2}{Molar mass of CO_2}$

$n_{CO_2}=\dfrac{312}{44}=7.09$ moles $=7.10$ moles (approx.)

As from the stoichiometry we can easily see that 1 mol of $CO_2$ achieved from 1 mol of $CH_4$ ,so $7.10$ moles achieved from $7.10$ moles of $CH_4$

So moles of $CH_4=7.10$ moles

mass of $CH_4=$ moles of $CH_4\times$ molar mass of $CH_4$

$=7.10\times16=113.16$ gm