Question

Consider that a sample of a compound is decomposed and the masses of its constituent elements is as follows: 1.443 g Se, 0.5848 g O What would be the empirical formula for this compound?

Answer 1

Answer: The empirical formula is $SeO_2$.

Explanation:

So, the mass of each element is given:

Mass of Se = 1.443 g

Mass of O = 0.5848 g

Step 1 : convert given masses into moles.

Moles of Se=$\frac{\text{ given mass of Se}}{\text{ molar mass of Se}}= \frac{1.443g}{79g/mole}=0.018moles$

Moles of O = $\frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{0.5848g}{16g/mole}=0.036moles$

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

For Se = $\frac{0.018}{0.018}=1$

For O =$\frac{0.036}{0.018}=2$

The ratio of Se: O = 1: 2

Hence the empirical formula is $SeO_2$.