Question

Propane gas, C3H8(g) , is used for barbeques. If 12.3 g of propane is combusted completely in a sufficient supply of oxygen gas, what mass of carbon dioxide gas is produced?

Answer 1

Every hydrocarbon, when reacting with O2, will produce CO2 and water. The balanced equation for the reaction of propane gas with O2 is:

`C_3H_(8(g))+5O_(2(g))\rightarrow3CO_(2(g))+4H_2O_((g))`

We know, by the equation above, that 1 mole of C3H8 produces 3 moles of CO2. We can convert moles to mass by multiplying the respective number of moles by the molar mass of each substance (both molar masses, in this case, are 44g/mol), so we have:

`\begin{gathered} m(C3H8)=1*44=44g_{}_{} \\ m(CO2)=3*44=132g \end{gathered}`

So, we discovered that 44g of C3H8 would produce 132g of CO2. This is a fixed propotion, and we can use it to discover how many grams of CO2 will be produced by the combustion of 12.3g of C3H8:

`\begin{gathered} 44\text{ g of C3H8----132 g of CO2} \\ 12.3\text{ g of C3H8---- x} \\ \\ x=(132*12.3)/(44)=36.9\text{ g of CO2} \end{gathered}`

So, 36.9 g of CO2 will be produced in this reaction.