Question

Difficulty: MediumPressure Law (Gay-Lussac's Law of Temperature-Pressure)

A rigid metallic cylinder contains a fixed mass of gas at an initial pressure of 1.2 atm1.2\text{ atm} and a temperature of 27C27^\circ\text{C}. If the gas is heated until its temperature reaches 177C177^\circ\text{C} while the volume remains constant, what is the final pressure of the gas in atmospheres?

Answer: 1.8 atm

Answer

The final pressure of the gas is 1.8 atm1.8\text{ atm}.
Converting the temperatures to Kelvin (T1=300 KT_1 = 300\text{ K} and T2=450 KT_2 = 450\text{ K}) and applying Gay-Lussac's Pressure Law P1T1=P2T2\frac{P_1}{T_1} = \frac{P_2}{T_2} gives P2=1.2×450300=1.8 atmP_2 = 1.2 \times \frac{450}{300} = 1.8\text{ atm}.

Step-by-Step Solution

1
Convert given temperatures to the Kelvin scale
T1=300 KT_1 = 300\text{ K} and T2=450 KT_2 = 450\text{ K}
Gas laws require absolute temperature values measured in Kelvin (TK=tC+273T_K = t_C + 273).
2
Set up Gay-Lussac's Pressure Law proportion P1T1=P2T2\frac{P_1}{T_1} = \frac{P_2}{T_2}
P2=P1×T2T1=1.2×450300P_2 = P_1 \times \frac{T_2}{T_1} = 1.2 \times \frac{450}{300}
At constant volume, the pressure of a fixed mass of gas is directly proportional to its absolute temperature.
3
Perform the multiplication to determine the final pressure
P2=1.8 atmP_2 = 1.8\text{ atm}
Multiplying 1.21.2 by the ratio 1.51.5 yields 1.8 atm1.8\text{ atm}.

Key Concept

Pressure Law (Gay-Lussac's Law) states that for a given mass of gas at constant volume, the pressure is directly proportional to its absolute temperature in Kelvin (PTP \propto T).
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