Question

A person has a sample of compound which has a formula that is C4H9. What percent carbon by mass is the compound? *(Note this is not a real compound)*

Answer 1

The percent cabon in the compound is 84.22%.

1st) We need to calculate the molar mass of C4H9 with the atomic mass of carbon (C) and hydrogen (H). We can find the atomic mass in the Periodic Table of Elements:

- Carbon atomic mass: 12.01 g/mol

- Hydrogen atomic mass: 1 g/mol

The compound C4H9 has 4 carbon atoms and 9 hydrogen atoms:

(12.01 g/mol x 4) + (1 g/mol x 9) = 57.04 g/mol

So, compound C4H9 weighs 57.04g/mol.

2nd) We know that 57.04 g represents the 100% of C4H9, so with a mathematical Rule of Three we can calculate the percent carbon in C4H9 knowing that all the carbon in the molecule weighs 48.04g (12.04 g x 4):

`\begin{gathered} 57.04g-100\% \\ 48.04g-x=(48.04g\cdot100\%)/(57.04g) \\ \\ x=84.22\% \end{gathered}`

Finally, the percent cabon by mass in the compound is 84.22%.