Question

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

A sealed rigid glass flask contains carbon dioxide gas at a temperature of 7C7^\circ\text{C} and a pressure of 1.4 atm1.4\text{ atm}. If the flask is heated to a final temperature of 77C77^\circ\text{C} at constant volume, what is the new pressure exerted by the gas?

  1. 1.75 atm1.75\text{ atm}Answer
  2. B
    15.4 atm15.4\text{ atm}
  3. C
    1.12 atm1.12\text{ atm}
  4. D
    2.10 atm2.10\text{ atm}

Answer

The new pressure exerted by the gas is 1.75 atm1.75\text{ atm}.
According to Gay-Lussac's Pressure Law, the pressure of a fixed mass of gas at constant volume is directly proportional to its absolute temperature (P1/T1=P2/T2P_1/T_1 = P_2/T_2). Converting the temperatures to Kelvin (T1=7+273=280 KT_1 = 7 + 273 = 280\text{ K} and T2=77+273=350 KT_2 = 77 + 273 = 350\text{ K}) and solving for P2P_2 gives P2=1.4×350280=1.75 atmP_2 = 1.4 \times \frac{350}{280} = 1.75\text{ atm}.

Step-by-Step Solution

1
Convert initial and final temperatures from Celsius to Kelvin.
T1=7+273=280 KT_1 = 7 + 273 = 280\text{ K} and T2=77+273=350 KT_2 = 77 + 273 = 350\text{ K}.
Gas laws require absolute temperature in Kelvin for proportional relationship calculations.
2
Apply the Pressure Law (Gay-Lussac's Law).
P1T1=P2T2    P2=P1×T2T1\frac{P_1}{T_1} = \frac{P_2}{T_2} \implies P_2 = P_1 \times \frac{T_2}{T_1}.
For a fixed mass of gas at constant volume, pressure is directly proportional to absolute temperature.
3
Substitute the values to calculate the final pressure P2P_2.
P2=1.4×350280=1.4×1.25=1.75 atmP_2 = 1.4 \times \frac{350}{280} = 1.4 \times 1.25 = 1.75\text{ atm}.
Simplifying the fraction 350280=54=1.25\frac{350}{280} = \frac{5}{4} = 1.25 gives the final answer.

Key Concept

Pressure Law (Gay-Lussac's Law)
Rate this question