Question

How do you calculate the percentage composition of Carbon in `C_2H_6`?

Answer 1

It really is just asking you what a percent is, and you know that it is just a ratio of `"C"` to `"C"_2"H"_6`.

The molar mass of `"C"` is `"12.011 g/mol"` and the molar mass of `"C"_2"H"_6` is `12.011*2 + 1.0079*6 = "30.0694 g/mol"`.

So, knowing that `"C"_2` in `"C"_2"H"_6` means there are two carbons in the compound, we get:

`(2xx"12.011 g/mol C")/("30.0694 g/mol C"_2"H"_6)xx100%`

`= ("24.022 g/mol C"_2)/("30.0694 g/mol C"_2"H"_6)xx100%`

`= color(blue)(79.89% "C in C"_2"H"_6)`

CHALLENGE: What is the percent composition of `H` in the compound?