Chemistry 2 Gas Laws Word Problems

Question

1. A sample of ammonia gas occupies 20.4 mL at 558 mm Hg and 25.2oC. If the volume of the gas is changed to 56.8 mL at 55oC, what is the new pressure? Enter mm for unit.
2. A sample of carbon monoxide gas occupies 144 mL at 24.5oC and 466 mm Hg. If the volume of gas is changed to 50.5 mL at 780 mm Hg, what is the Kelvin temperature?
3. If a 50.2 mL sample of xenon gas is at 0.835 atm and 44oC, what is the volume of the gas at STP?
4. If the pressure of 135 mL of nitrogen gas at 100oC decreases from 776 mm Hg to 298 mm Hg, what is the final volume? Assume temperature remains constant.
5. A sample of carbon dioxide gas occupies 1.59 L at -20.4oC and 525 mm Hg. If the volume of the gas is changed to 2.73 L at 775 mm Hg, what is the final Kelvin temperature?
6. A sample of ozone gas occupies 231 mL at 3.92 atm and 0oC. If the volume of the gas is 619 mL at 32.9oC, what is the pressure? Enter mm for unit.

 

 

Answer 1

All of these problems involve using the Combined Gas Law, which states:

 

(p₁V₁)/T₁ = (p₂V₂)/T₂,

 

where p₁, V₁, and T₁ are the initial pressure, volume, and temperature of a gas and p₂, V₂, and T₂ are the pressure, volume, and temperature after some change is made to the gas.

 

 

All of these problems just give you five of those values and ask you to solve for the sixth. The first problem, for example, tells you that, initially, V₁ = 20.4 mL, p₁ = 558 mm Hg, and T₁ = 25.2 C. It tells you that, after some change, V₂ = 56.8 mL and T₂ = 55 C. It asks you to solve for p₂. You'll just need to plug in those numbers and solve.

 

Each problem works the same way. Just be careful to keep an eye out for changing units. In problem 2, for example, you're given T₁ in C and asked for T₂ in K. Just find T₂ in C and then convert to K.