Question

A sample of trifluoroacetic acid, C2HF3O2, contains 26.5 g of oxygen. Calculate the mass of the trifluoroacetic acid sample.

Answer 1

Answer:

94.3 grams

Explanation:

MW of C2HF3O2 is 114g/mol

MW of oxygen in C2HF3O2 is 32g/mol

% composition of oxygen in C2HF3O2 = 32/114 × 100 = 28.1%

Mass of oxygen = 26.5 grams

Mass of trifluoroacetic acid = 26.5/0.281 = 94.3 grams

Answer 2

Answer:

94.406 grams of the trifluoroacetic acid sample.

Explanation:

Mass of oxygen in trifluoroacetic acid = 26.5 g

Moles of oxygen = $\frac{26.5 g}{16 g/mol}=1.65625 mol$

1 mole of trifluoroacetic acid has 2 moles of oxygen element.

Then n moles of trifluoroacetic acid have 1.65625 mole of oxygen element.

$n\times 2=1.65625 mol$

$n=\frac{1.65625 mol}{2}=0.828125 mol$

Mass of 0.828125 moles of trifluoroacetic acid = m

Molar mass trifluoroacetic acid = M = 114 g/mol

$m=n\times M=0.828125 mol\times 114 g/mol=94.406 g$

94.406 grams of the trifluoroacetic acid sample.