Question

A chromium oxide compound contains 104.0 grams of chromium and 48.0 grams of oxygen. What is the most likely empirical formula of this compound?

Answer 1

Answer: Empirical formula of this compound is $Cr_2O_3$

Explanation:

Mass of Cr= 104.0 g

Mass of O = 48.0 g

Step 1 : convert given masses into moles.

Moles of Cr =$\frac{\text{ given mass of Cr}}{\text{ molar mass of Cr}}= \frac{104.0g}{52g/mole}=2moles$

Moles of O =$\frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{48.0g}{16g/mole}=3moles$

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For Cr = $\frac{2}{2}=1$

For O =$\frac{3}{2}=1.5$

Converting into simple whole number ratios by multiplying by 2

The ratio of Cr : O= 2: 3

Hence the empirical formula is $Cr_2O_3$

The most likely empirical formula of this compound is $Cr_2O_3$