Chapter 5 Flashcards
What are the assumptions of an ideal gas?
1) volume of the gas relative to the size of the container it is in is insignificant - most accurate at low pressures
2) collisions are perfectly elastic - most accurate at high temperatures and weak intermolecular forces
3) average kinetic energy of the gas depends on the temperature
Boyle’s Law
Volume and pressure are inversely related
Charle’s Law
Volume and temperature are proportional
Avagadro’s Law
Volume is proportional to n, the number of moles of gas
The ideal gas law is most accurate when gases are behaving ideally; ____ temperatures and ____ pressures
high, low
Density formula
D = (pressure x molecular mass) / (R)(T)
Dalton’s Law
The total pressure of gasses is equal to the sum of all individual pressures of each gas
Compare and contrast ideal gases and real gases
Real gases have a defined volume and intermolecular forces, where as ideal gases do not
Identify what (nb) and (an2/v2) correct for in the van Der walls real gas equation correct for.
nb - corrects for repulsions
an2/v2 - corrects for intermolecular forces
The mole fraction of all components in a mixture adds up to _____
1
Consider two gases: 1.0 mol of He in a 1.0 L container at 25 oC, and 2.0 mol of Ne in a 1.0 L container at 25 oC. Which of the following statements is true regarding these two gases? Assume both gases obey ideal gas behaviors.
I. Molecules of He travel faster than molecules of Ne.
II. The gas molecules of Ne have a higher average kinetic energy than those of He.
III. The two gases have the same pressure.
A. I and III only B. I only C. II and III only D. I and II only E. I, II, and III
B
Explanation - Kinetic energy is only changed if temperature is changed; thus II is wrong. The gases actually have different pressures because there is twice as many mols of Ne than He.
A gas cylinder containing an unknown gas and methane, CH4, developed a leak. The unknown gas was found to effuse half as fast as methane. Which of the following could be the unknown gas?
A) He B) NH3 C) SO2 D) N2 E) NO2
Use grahams law of effusion!
C
A flask contains 5.5 mol of O2 gas at 25 oC and 2.00 atm. How much O2 gas, in moles, must be added to increase the pressure to 8.00 atm at constant temperature and volume?
Use the p1V1 = p2V2 equation and solve for n2. Subtract 5.5 from 22 to get 16.5
A sample of an ideal gas at 298K and 3 atm has a volume of 2.5 L. What will be the volume of the same sample of gas at 1 atm pressure and 298K? A. 0.8 L B. 5.0 L C. 2.5 L D. 7.5 L E. 12 L
At constant temperature and amount of gas, pressure is inversely proportional to volume. If pressure decreases to 1/3 its initial amount (3 atm → 1 atm), the volume will increase by 3 times. Therefore, the new volume will be 7.5 L.
How to find partial pressure?
the partial pressure of a gas in a mixture is also equal to the mole fraction of that gas times the total pressure of the mixture
