Copper(II) oxide (\text{CuO}) is a black solid compound formed when copper metal is strong… — JAMB UTME

Copper(II) oxide ( $\text{CuO}$ ) is a black solid compound formed when copper metal is strongly heated in air. Given the relative atomic masses of copper ( $\text{Cu} = 64$ ) and oxygen ( $\text{O} = 16$ ), what is the percentage by mass of copper in pure copper(II) oxide?

Answer: 80 %

Answer

The percentage by mass of copper in pure copper(II) oxide (

\text{CuO}

) is

80\%

The molar mass of copper(II) oxide (

\text{CuO}

) is

64 + 16 = 80\text{ g/mol}

. The relative mass contributed by copper is

64\text{ g/mol}

. Dividing

64

80

and multiplying by

100

gives

80\%

Step-by-Step Solution

Calculate the molar mass of copper(II) oxide (

\text{CuO}

Molar mass of

\text{CuO} = 64 + 16 = 80\text{ g/mol}

The molar mass of a binary compound is the sum of the relative atomic masses of its constituent elements.

Calculate the mass percentage of copper in the compound.

\text{Percentage of Cu} = \left(\frac{64}{80}\right) \times 100\% = 80\%

The mass percentage is found by dividing the mass contributed by copper by the total molar mass of the compound and multiplying by 100.

Key Concept

Percentage composition by mass of an element in a copper compound

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