Question

1. A sample of gas with an initial volume of 28.2 L at a pressure of 728 mmHg and a temperature of 301 K is compressed to a volume of 14.9 L and warmed to a temperature of 375 K. What is the final pressure of the gas?

2. A gas sample with a volume of 5.3 L has a pressure of 725 mmHg at 24C. What is the pressure of the sample if the volume remains at 5.3 L but the temperature rises to 88 ∘C?

3. What is the volume occupied by 0.256 mol of helium gas at 1.20 atm and 303 K ?

4. A cylinder contains 28.5 L of oxygen gas at a pressure of 1.6 atm and a temperature of 300 K . How many moles of gas are in the cylinder?

Express your answer using two significant figures.

5. An experiment shows that a 266 mL gas sample has a mass of 0.428 g at a pressure of 765 mmHg and a temperature of 30 ∘C. What is the molar mass of the gas?

Answer 1

1. We know Ideal gas equation PV=nRT

Now for the two conditions let P1, V1, T1 be pressure, volume, temperature for initial condition and P2, V2, T2 be pressure, volume, temperature for final condition.

So, P1*V1/T1=P2*V2/T2 (equation 1)

Here, P1=728 mm Hg, V1= 28.2 L, T1= 301 K and P2= ?, V2= 14.9 L, T2= 375 K.

On putting value in equation 1

(728 mm Hg)*(28.2 L)/(301 K) = P2*(14.9 L)/(375 K).

P2 = 1716.56 mm Hg.

2. According to Gayy Lussac's Law, at constant Volume, Pressure is directly proportional to Temperature.

So, P1/T1=P2/T2

Here, P1= 725 mm Hg, T1=24 °C, P2= ?, T2= 88 °C

On putting values in above equation

(725 mm Hg)/(24 °C) = P2/(88 °C)

P2= 197.73 mm Hg