Question

Find the formula mass of the compound, then divide the individual element total by the total mass-move the decimal over two to change it to percentage Al2O3

Answer 1

1) Find the formula mass of Al2O3.

Aluminum mass: 26.982 u.

Oxygen mass: 15.999 u.

Al2O3 mass = 2 * (26.982 u) + 3 * (15.999 u)

Al2O3 mass = 101.961 u.

2) Aluminum percentage.

Aluminum mass: 26.982 u.

Al2O3 mass = 101.961 u.

`\frac{(2*26.982\text{ }u)}{101.961\text{ }u}=0.5293`

Moving the decimal point.

52.93%

The percentage of aluminum is 52.93%

3) Oxygen percentage.

Oxygen mass: 15.999 u.

Al2O3 mass = 101.961 u.

`\frac{(3*15.999\text{ }u)}{101.961\text{ }u}=0.4707`

Moving the decimal point.

47.07%

The percentage of oxygen is 47.07%.

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