Question

How many moles of methane are required to produce 22 g $C{O_2}$ after combustion?

Answer 1

To solve this question, we need to know the balanced equation in which methane will combust to produce carbon dioxide and water.
$C{H_4} + 2{O_2} \to C{O_2} + 2{H_2}O$
By using this equation and the mole concept we will be able to solve this question. We can say that one mole of methane will combust to give one mole of carbon dioxide.

Complete answer:
We can say that the gram molecular mass of $C{O_2}$ can be calculated as the mass of the carbon atom and the mass of two oxygen atoms. Thus we can say that the gram molecular mass of $C{O_2}$ is going to be 44 g/mol.
We can say that 1 mole of methane can produce one mole of carbon dioxide on complete combustion and therefore we can say that 1 mole of methane on complete combustion produces 44 grams of carbon dioxide.
Therefore we have to calculate the number of moles of methane required to produce 22 grams of carbon dioxide.
If 1 mole produces 44 g, x moles will produce 22 g.
Cross multiplying the values we get:
$\Rightarrow x = \dfrac{1}{{44}} \times 22 = 0.5\;mol$
Thus we can say that 0.5 moles of methane on complete combustion will produce 22 grams of carbon dioxide.

Note:
In questions that deal with the number of moles of reactants or products, always write down the complete balanced equation first. This will give us an idea about how we have to approach the problem. In the case of complicated equations only look at the stoichiometry of the required chemicals in the questions.