A 2.241-g sample of nickel reacts with oxygen to form 2.852 g of the metal oxide. Calculate the empirical formula of the oxide?

NiO

Explanation:

Firstly, we need to know the mass of oxygen used up. This is the difference between the mass of the nickel and the mass of the oxide. This is : 2.852 - 2.241 = 0.611g

Now we convert these masses to mole by dividing by their atomic masses. The atomic mass of oxygen is 16 while that of nickel is 59

O = 0.611/16 = 0.0381875

Ni = 2.241/59 = 0.037983050847458

The next thing is to divide each by the smaller number of moles, which is that of the nickel.

O = 0381875 / 0.037983050847458 = 1

Ni = 0.037983050847458/0.037983050847458 = 1

The empirical formula is thus NiO