Chemistry 2010 JAMB Past Questions - Question 5: The volume of a given gas is Vcm³ at P mmHg. What is the new volume of the gas if the pressure is reduced to half at constant temperature?

Correct Answer

B

Explanation

when the pressure is reduced to half, the volume is doubled.
Since the temperature is **constant**, we can utilize **Boyle's Law**, which states that for an ideal gas at constant temperature, the pressure and volume are inversely proportional. This means:

**P? × V? = P? × V?**

where:

* P? is the initial pressure (P mmHg)
* V? is the initial volume (V cm³)
* P? is the final pressure (half of P mmHg, so P/2 mmHg)
* V? is the final volume (unknown)

We want to find V?, so let's rearrange the equation:

**V? = (P? × V?) / P?**

Substitute the known values:

**V? = (P × V) / (P/2)**

**V? = (P × V × 2) / P**

Cancel out the P on both sides:

**V? = (V × 2)**

**V? = 2V**

Therefore, the new volume of the gas is **2Vcm³**.

So the answer is 2Vcm³