Question

Propane is used as a fuel in most gas grills to cook food on during the warm summer months. When the propane is burned the following reaction takes place:
C3H8(l) + 5O2(g) = 3CO2(g) + 4H20(g)

A standard propane tank contains 6804 g of propane. Determine how many molecules of carbon dioxide gas are released into the atmosphere with an entire tank of propane is burned. In your answer be sure to: Describe the type of chemical reaction the propane undergoes, calculate the number of moles of propane used in the reaction, explain the mole ratio between propane and carbon dioxide in this reaction, calculate the number of moles of carbon dioxide produced, and calculate the number of molecules of carbon dioxide produced.

Answer 1

The propane undergoes a combustion reaction (combustion reactions are reactions in which a substance reacts with oxygen and burns).

To calculate the number of moles of propane, we use the molar mass of propane, which is 44.0 g/mol.

$(6804g\ C_3H_8)(\frac{1mol\ C_3H_8}{40.0g\ C_3H_8})=170.1mol\ C_3H_8$

To convert mol C3H8 into mol CO2, we use the molar ratio between the two substances. The molar ratio is seen by the coefficients in front of the each substance in the reaction, so the ratio of C3H8 to CO2 is 1 to 3, with 3 moles of CO2 produced for every mole of C3H8 reacting.

$(170.1mol\ C_3H_8)(\frac{3mol\ CO_2}{1mol\ C_3H_8})=510.3mol\ CO_2$

To convert mol CO2 into molecules of CO2, we use Avogadro's number:
There are 6.022 × 10²³ molecules per mole of any substance:

$(510.3mol\ CO_2)(\frac{6.022*10^{23}mlcs\ CO_2}{mol\ CO_2})=3.07*10^{26}molecules\ CO_2$