Question

How many litres of carbon dioxide are produced when $ 2.0 $ moles of $ C{H_4} $ are burned at $ STP $ ?

Answer 1

Hint: Write down the chemical equation of the combustion reaction for $ C{H_4} $ and balance it. After balancing, find out the mole-to-mole ratio of $ C{H_4} $ and $ C{O_2} $ . We will also use the concept of $ STP $ , that is, $ 1 $ mol of a gas occupies $ {\text{22}}{\text{.4}} $ litres of volume at $ STP $ . The mole-to-mole ratio and $ STP $ factor will help us in finding the litres of $ C{O_2} $ produced on burning of $ {\text{2}} $ moles of $ C{H_4} $ .

Complete answer:
When methane $ (C{H_4}) $ undergoes combustion, then the following reaction takes place where methane on burning gives carbon dioxide as well as hydrogen.
 $ C{H_4} + 2{O_2}\xrightarrow{\Delta }C{O_2} + 2{H_2}O $
From the balanced equation above, we can see that the mole ratio of $ C{H_4}:C{O_2} $ is $ 1:1 $ or that $ 1 $ mol of $ C{H_4} $ gives $ 1 $ mol of $ C{O_2} $ . Therefore, on burning $ {\text{2}} $ moles of $ C{H_4} $ , it will produce $ {\text{2}} $ moles of $ C{O_2} $ .
Now, at $ STP $ , $ {\text{1}} $ mol of a gas occupies a volume of $ {\text{22}}{\text{.4}} $ litres or we can say that $ {\text{1 mol}} $ of a gas is equal to $ {\text{22}}{\text{.4}} $ litres of that gas. Since, $ {\text{1 mol}} $ of $ C{H_4} $ on burning gives $ 1 $ mol of $ C{O_2} $ , we can say that we get $ {\text{22}}{\text{.4}} $ litres of $ C{O_2} $ . Thus, when $ {\text{2}} $ moles of $ C{H_4} $ is burned, $ {\text{2}} $ moles of $ C{O_2} $ will pe produced or we can say that $ 2 \times 22.4 = 44.8 $ litres of $ C{O_2} $ will be produced.
Hence, when $ {\text{2}} $ moles of $ C{H_4} $ is burned, $ 44.8 $ litres of $ C{O_2} $ will be produced.

Note:
Balancing of the chemical equation should be performed carefully. Any error in balancing will influence the mole-to-mole ratio of $ C{H_4} $ and $ C{O_2} $ which will ultimately result in an incorrect solution. Keep in mind the $ STP $ factor of $ 22.4Lmol{e^{ - 1}} $ . Also, pay close attention to the units while writing the solution.