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WAEC Chemistry 2025 Paper

Question : 6

Total: 50

^3

^3

Solution:

Concept:

Use the combined gas law:

\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}

Explanation:

List the given values:

P_1 = 1\ \text{atm}

V_1 = 400\ \mathrm{cm^3}

T_1 = 400\ \mathrm{K}

, and

V_2 = 200\ \mathrm{cm^3}

Substitute into the combined gas law:

\frac{1 \times 400}{400} = \frac{P_2 \times 200}{T_2}

Simplify the left side:

1 = \frac{200P_2}{T_2}

Rearrange to get

\frac{T_2}{P_2} = 200

Test each option using

T_2 = 200P_2

For Option C,

T_2 = 200\ \mathrm{K}

and

P_2 = 1\ \text{atm}

gives

200 = 200 \times 1

, which is correct.

The other options do not satisfy the required relation.

Answer:

200\ \mathrm{K}

and

1\ \text{atm}

, i.e., Option C.

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