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JAMB Chemistry 2023 Paper

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Question : 39

Total: 82

What is the mass percentage of carbon (C) in methane (CH4)? (The molar mass of carbon is approximately 12 g/mol.)

25%
12%
75%
50%

Solution:

Concept:

Mass percentage is the mass of a specific element divided by the total molar mass, multiplied by 100%.

Explanation:

The molar mass of methane (

\mathrm{CH}_4

) is

12 \, \text{g/mol}

(carbon) plus

4 \times 1 \, \text{g/mol}

(hydrogen).

So, molar mass of

\mathrm{CH}_4 = 12 + 4 = 16 \, \text{g/mol}

.

Mass percentage of carbon is:

\frac{12 \, \text{g/mol}}{16 \, \text{g/mol}} \times 100\% = 75\%

.

Answer:

C. 75%

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