Page 23 - Surviving Chemistry BFF Homework Helper and Test Prep Preview

Relates pressure (P), volume (V), temperature (T)
and the number of moles (n) of a gas.

A 5.0 L sample of an ideal gas at 310 K exerts a
PV = nRT
pressure of 2.0 atm on the walls of its container.
R = the universal gas constant, What is the number of moles of the gas?
.
.
0.0821 L atm /( mol K)

PV (2.0) (5.0)
n = ------- = ------------------ = 0.39 moles
RT (0.0821) (310)

Under the same conditions of temperature and
pressure, the rate (speed) at which gases effuse
(escape through a pinhole) is inversely

r1 M2 proportional to the square root of their

--- = ------ molecular mass (M).

r2 M1
How much faster does hydrogen gas, H2,
escape through a hole of a container than sulfur

dioxide, SO2 ?
r 1 = rate (speed) of Gas 1
r 2 = rate (speed) of Gas 2 rH mass of SO2 64 g
2
M 1 = molecular mass of Gas 1 ----- = --------------- = ------ = 5.63 times
M 2 = molecular mass of Gas 2 rSO mass of H2 2 g
2
The calculated result shows that the lighter gas,
H2, travels 5.63 time faster than the heavier gas,
SO2.

Additional materials Practice Questions

o
28. How many moles of an ideal gas take up 35 L of volume at 25 C and 1.5 atm?

29. 2.39 moles of an ideal gas at 300 K occupy 29.0 L . What is the pressure?

30. 0.105 moles of an ideal gas occupy 5.00 L at a pressure of 0.975 atm. What is
the temperature of the gas in Kelvin?

31. Of these gases; SO2, CO, HCl, and NO2 .

a) Which will travel the fastest? b) Which will travel the slowest?

32. How much faster does NO(g) effuse in comparison to N2O5(g)?

33. Calculate the rate of effusion of NO2 in comparison to SO2 at the same

temperature and pressure.

34. An unknown gas effuses 1.66 times more rapidly than CO2.
What is the molar mass of the unknown gas?

35. A sample of hydrogen gas effuses through a porous container 9 times faster

than an unknown gas. Estimate the molar mass of the unknown gas.

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