A compound of 2.225 g, known to be a carbohydrate, was analyzed and found to contain 0.890 g of carbon, 0.148 g of hydrogen and the rest was oxygen. How do you determine the percentage composition by mass of the compound?

May 19, 2017

40.0% C
6.65% H
53.3% O

Explanation:

The mass percentage of a substance in a compound is represented by the equation

%compon ent = (g_(compon ent))/(g_(t otal)) xx 100%

What we can do first is find it how much $O$ is present, by subtracting the sum of the masses of $C$ and $H$ from the total mass:

${g}_{{O}_{2}} = 2.225 g - \left(0.890 g + 0.148 g\right) = 1.187 {g}_{{O}_{2}}$

Now, let's use the above formula to calculate the percentage by mass of each component:

%C = (0.890g)/(2.225g) xx 100% = 40.0%

%H = (0.148g)/(2.225g) xx 100% = 6.65%

%O = (1.187g)/(2.225g) xx 100% = 53.3%