Question

What is the mass percent of carbon in propanoic acid (C2H5COOH)? (The molar mass of C = 12.01, H = 1.0079, and O = 16.00.)

1. 43.20%
2. 43.79%
3. 48.64%
4. 51.56%
5. 52.41%

Answer 1

The mass percent of carbon in propanoic acid is 48.64 % (answer 3)

calculation

mass percent = [(mass of carbon in propanoic /mass of propanoic) x100]

mass of carbon in propanoic = (12.01 x2) + 12.01 = 36.03

mass of propanoic =( 12.01 x2) +( 1.0079 x5) +12.01 +16 +16 + 1.0079 =74.0774

mass percent = 36.03 /74.0774 x 100 = 48.64%

Answer 2

Mass percent is calculated by the ratio of the mass of the substance in a sample over the total mass of the sample multiplied by 100. Assuming 1 mol of the acid, we will have 74.09 g. We do as follows:

% by mass C = 3 ( 12.01) / 74.09 x 100 = 48.63% C