Answer to Question #86556 in General Chemistry for thomas

Question

A sample of hydrogen gas at 299 K and 0.785 atm occupies a volume of 2.67 L. If the gas is allowed to expand to a larger volume , while at the same time it is heated to a higher temperature, the final gas pressure

A. will be higher than 0.785 atm.
B. will be lower than 0.785 atm.
C. could be higher or lower than 0.785 atm depending on the final volume and temperature.

Answer 1

Clapeyron-Mendeleev equation for ideal gas is

$PV= \frac{m}{M} RT$ ,

where P – gas pressure; V – gas volume; m and M - mass and molar mass of the gas, respectively; R – gas constant, T – gas temperature.

m and M are constant under the considered conditions, so $\frac{PV}{T}=const$. Simultaneous increase in volume and temperature leads to the ambiguity in the change of the pressure. It could increase or decrease depending on the final volume and temperature.

Answer: C. could be higher or lower than 0.785 atm depending on the final volume and temperature.