HC Gases & Thermo Review

Gas pressure is caused by

• gas molecules colliding with surfaces
• gas molecules condensing to a liquid
• gas molecules hitting other gas molecule
• an outside force on the outside of the container

At a constant pressure, the volume increases. What happens to the temperature?

• increases

• decreases

• stays the same

At a constant temperature, pressure decreases. What happens to the volume?

• increases

• decreases

• stays the same

If the reaction below takes place in a sealed, rigid container, does pressure increase or decrease at the end of the reaction? Assume temperature is constant.

2 NH₃ (g) --> N₂ (g) + 3 H₂ (g)

• Increase

• Decrease

• Stay the same

• Can't be determined

What is the pressure in atmospheres (atm) of a 0.34 mol sample of helium gas at a temperature of 20.0 degrees C if its volume is 0.820 L?

• 0.68 atm

• 9.97 atm

• 1.47 atm

• 0.10 atm

Only O₂ and H₂ in a container. If the total pressure is 3.4 atm and the mole fraction of O₂ is 0.42, what is the partial pressure of H₂?

• 0.58 atm

• 3.4 atm

• 1.43 atm

• 1.97 atm

Which of the following gases will diffuse the quickest:

N₂, CH₄, O₂, Ne

• CH₄

• Ne

• N₂

• O₂

Helium effuses 3.16 times faster than which other noble gas? (Hint: use Graham's Law to calculate the missing molar mass - then compare with a periodic table!)

• Ne

• Ar

• Kr

• Xe

In an endothermic reaction the system is absorbing energy.

• True
• False

Select all that apply: which of the following processes is (are) endothermic?

• BCl₃ + 3 H₂O → H₃BO₃ + 3 HCl ΔH = -112 kJ

• Ice in your glass of water melts on a hot summer day.

• 2 HgO + 181 kJ → 2 Hg + O₂

• When a solid dissolves in water, the temperature of the water increases.