Physics 2001 JAMB Past Questions - Question 16: The pressure of a given mass of a gas changes from 300 Nm-² to 120 Nm-²

Correct Answer

B

Explanation

To calculate the change in pressure of a given mass of gas, you can use the ideal gas law, which relates pressure (P), volume (V), the number of moles of gas (n), and the gas constant (R) to the temperature (T) of the gas. The ideal gas law is typically written as:

PV = nRT

Where:
P = Pressure (in pascals, Pa)
V = Volume (in cubic meters, m³)
n = Number of moles of gas
R = Ideal gas constant (8.314 J/(mol·K) for SI units)
T = Absolute temperature (in kelvin, K)

If you're given the pressure in N/m² (which is equivalent to pascals), you can use this unit in the ideal gas law directly.

To find the change in pressure, you'll want to calculate the initial and final values using the ideal gas law:

Initial pressure (P1) = 300 N/m² = 300 Pa
Final pressure (P2) = 120 N/m² = 120 Pa

Now, you can calculate the change in pressure (ΔP) as:

ΔP = P2 - P1
ΔP = 120 Pa - 300 Pa
ΔP = -180 Pa

So, the pressure of the given mass of gas has changed by -180 pascals. The negative sign indicates a decrease in pressure from 300 Pa to 120 Pa.