Question

Calculate the percent composition of Cr2O3

Answer 1

Cr 2(52.0) = 104 O 3(16.0) = 48
104/152 * 100 = 68.42% Cr
48/152 * 100 = 31.58% O

Answer 2

Explanation:

Percentage of an element in a compound:

$\frac{\text{Number of atoms of element}\times \text{Atomic mass of element}}{\text{molecular mass of compound}}\times 100$

Molecular mass of $Cr_2O_3$ = 152 g/mol

Percentage of chromium:

Number of chromium atoms = 2

Atomic mass of chromium = 52 g/mol

$\frac{2\times 52g/mol}{152g/mol}\times 100=68.42\%$

Percentage of oxygen:

Number of oxygen atoms = 3

Atomic mas of oxygen = 16 g/mol

$\frac{3\times 16g/mol}{152 g/mol}\times 100=31.58\%$

The percent composition of Cr in $Cr_2O_3$ is 68.42%.

The percent composition of O in $Cr_2O_3$ is 31.58%.