1. An oxide of chromium is found to have the following % composition: 68.4% Cr and 31.6% 0. Determine this compound's empirical formula.

Empirical formula is Cr₂O₃.

Explanation:

Given data:

Percentage of Cr = 68.4%

Percentage of O = 31.6%

Empirical formula = ?

Solution:

Number of gram atoms of Cr = 68.4 / 52 = 1.3 2

Number of gram atoms of O = 31.6 / 16 = 1.98

Atomic ratio:

                            Cr               :         O

                           1.32/1.32     :       1.98/1.32

                               1              :        1.5

Cr : O = 1 :  1.5

Cr : O = 2(1 : 1.5)

Empirical formula is Cr₂O₃.

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