Question

When 2.5 liters of oxygen gas reacts with excess methane, how many liters of carbon dioxide is produced?

Answer 1

Stoichiometry tells us the method to calculate the unknown amount of substances, using the molecular coefficient from a balanced chemical equation.

Complete answer: We have been given that methane reacts with oxygen, where oxygen has volume 2.5 liters. We have to find out the amount of carbon dioxide produced.
As we know, combustion of hydrocarbons yields carbon dioxide and water. So, the chemical equation for the reaction of methane with oxygen will be,
$C{{H}_{4}}(g)+2{{O}_{2}}(g)\to C{{O}_{2}}(g)+2{{H}_{2}}O(g)$
As the equation suggests, when 2 moles of oxygen reacts with methane, then 1 mole of carbon dioxide is produced. Now, for a given gas at equal temperature and pressure, equal numbers of molecules are there in equal amounts of the gas. So, using stoichiometric and unitary method we will get the volume of carbon dioxide produced as,
Amount of $C{{O}_{2}}$in 2.5 L ${{O}_{2}}$= $\dfrac{1\,mole\,of\,C{{O}_{2}}}{2\,moles\,of\,{{O}_{2}}}\times 2.5\,L\,C{{O}_{2}}$
Amount of $C{{O}_{2}}$in 2.5 L ${{O}_{2}}$= $\dfrac{1\,mole\,}{2\,mole}\times 2.5\,L\,$
Amount of $C{{O}_{2}}$in 2.5 L ${{O}_{2}}$= $\dfrac{2.5\,L}{2}$
Amount of $C{{O}_{2}}$in 2.5 L ${{O}_{2}}$= 1.25 L
Hence, the volume of carbon dioxide produced from 2.5 liters of oxygen is 1.25 liters.

Note: When combustion occurs, any substance will react with oxygen, and hydrocarbons yield carbon dioxide and water when combustion is complete. While when incomplete combustion occurs, carbon monoxide is formed due to lack of oxygen. Equal volume of gases has equal number molecules at same condition of temperature and pressure, is the Avogadro’s Law of gases.