Chemistry Examples Molecules and Compounds

Find the Mass Percentages

$K O_{2}$

Step 1

To find the mass of $1$ mole of $K O_{2}$ look up the atomic mass of each element and multiply it by the number of atoms contained in each element in the molecule.

mass of $1$ mole of $K O_{2}$ $=$ $(mass of K)$ + $2 (mass of O)$

Step 2

Fill in the atomic masses from the periodic table.

mass of $1$ mole of $K O_{2}$ $=$ $(39.09999847)$ + $2 (16)$

Step 3

Simplify the result.

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Step 3.1

Multiply $2$ by $16$ .

mass of $1$ mole of $K O_{2} = 39.09999847 + 32 g$

Step 3.2

Add $39.09999847$ and $32$ .

mass of $1$ mole of $K O_{2} = 71.09999847 g$

Step 4

Find the mass percentage of $K$ .

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Step 4.1

The mass composition percentage is the mass of $K$ divided by the mass of the entire molecule converted to a percentage.

Mass percentage of $K = \frac{39.1}{71.09999847} \cdot 100$

Step 4.2

Divide $39.1$ by $71.09999847$ .

$0.54992968 \cdot 100$

Step 4.3

Multiply $0.54992968$ by $100$ .

$54.99296883$

Step 4.4

Set the number as a percent.

Mass percentage of $K = 54.99296883 %$

Step 5

Find the mass percentage of $O$ .

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Step 5.1

The mass composition percentage is the mass of $O$ divided by the mass of the entire molecule converted to a percentage.

Mass percentage of $O = \frac{32}{71.09999847} \cdot 100$

Step 5.2

Divide $32$ by $71.09999847$ .

$0.45007033 \cdot 100$

Step 5.3

Multiply $0.45007033$ by $100$ .

$45.00703331$

Step 5.4

Set the number as a percent.

Mass percentage of $O = 45.00703331 %$

Step 6

Find the mass percentage of each element in the molecule.

Mass percentage of $K = 54.99296883 %$

Mass percentage of $O = 45.00703331 %$

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