# Question c8827

Feb 11, 2017

1.8g

#### Explanation:

First, you must write out the balance combustion reaction in order to know how the carbon and oxygen are combined. Assuming we are starting with elemental carbon and burning it with pure oxygen, the equation is:

C + O_2 → CO_2#

So, every mole of carbon requires one mole of oxygen and produces one mole of carbon dioxide.

6.6g $\frac{C {O}_{2}}{44 \text{g/mol}}$ = 0.15 mol $C {O}_{2}$
Therefore we require 0.15 mole of carbon.

0.15 mol * 12 g/mol = 1.8g carbon.

An alternative way to calculate the amount is to look at the product mass only. $C {O}_{2}$ has a molecular weight of 44g/mol. The mass ratio of the carbon to carbon dioxide is 12C/44$C {O}_{2}$, or 0.273. Use this ratio to calculate the mass of carbon: 0.273 * 6.6 = 1.8.
This alternative procedure may not work with more complex reactions.