AP CHEM FINAL STUDYGUIDE
A flask contains 0.25 mole of SO2(g), 0.50 mole of CH4(g), and 0.50 mole of O2(g). The total pressure of the gases in the flask is 800 mm Hg. What is the partial pressure of the SO2(g) in the flask?
160 mmHg
A sealed vessel contains 0.200 mol of oxygen gas, 0.100 mol of nitrogen gas, and 0.200 mol of argon gas. The total pressure of the gas mixture is 5.00 atm. The partial pressure of the argon is
2.00 atm
An equimolar mixture of N2(�) and Ar(�) is kept inside a rigid container at a constant temperature of 300 K. The initial partial pressure of Ar in the mixture is 0.75atm. An additional amount of Ar was added to the container, enough to double the number of moles of Ar gas in the mixture. Assuming ideal behavior, what is the final pressure of the gas mixture after the addition of the Ar gas?
2.25atm, because doubling the number of moles of Ar doubles its partial pressure.
A 2 L sample of N2(g) and a 1 L sample of Ar(g), each originally at 1 atm and 0°C, are combined in a 1 L tank. If the temperature is held constant, what is the total pressure of the gases in the tank?
3 atm
A sample of carbonate rock is a mixture of CaCO3 and MgCO3. The rock is analyzed in a laboratory, and the results are recorded in the table above. Which columns in the table provide all the information necessary to determine the mole ratio of Ca to Mg in the rock?
3. 4. 6. 7.
When 6.0 L of He(g) and 10. L of N2(g), both at 0oC and 1.0 atm, are pumped into an evacuated 4.0 L rigid container, the final pressure in the container at 0oC is
4.0 atm
The figure above represents three sealed 1.0 L vessels, each containing a different inert gas at 298 K. The pressure of Ar in the first vessel is 2.0 atm. The ratio of the numbers of Ar, Ne, and He atoms in the vessels is 2:1:6, respectively. After all the gases are combined in a previously evacuated 2.0 L vessel, what is the total pressure of the gases at 298 K?
4.5 atm
A 2 L container will hold about 4 g of which of the following gases at 0°C and 1 atm?
5 atm
The pressure, in atm, exerted by 1.85 mol of an ideal gas placed in a 3.00 L container at 35.0°C is given by which of the following expressions?
A) (1.85)(0.0821)(308)/3.00
On the basis of the data provided above, the gas in container 3 could be
A) CH4
A gas mixture at 0°C and 1.0atm contains 0.010mol of H2, 0.015mol of O2, and 0.025mol of N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture?
About 0.20atm, because H2 comprises 20% of the total number of moles of gas.
A rigid metal tank contains oxygen gas. Which of the following applies to the gas in the tank when additional oxygen is added at constant temperature?
C The average speed of the gas molecules remains the same
Which flask contains the sample with the greatest density?
C) 40 degrees and 20 atm
A 2 L container will hold about 4 g of which of the following gases at 0°C and 1 atm?
CO2
A sample of an unknown gas from a cylinder is collected over water in the apparatus shown above. After all the gas sample has been collected, the water levels inside and outside the gas collection tube are made the same. Measurements that must be made to calculate the molar mass of the gas include all of the following EXCEPT
E) mass of water on the apparatus
The synthesis of CH3OH(g) from CO(g) and H2(g) is represented by the equation above. The value of Kc for the reaction at 483 K is 14.5. A mixture of CO(g) and H2(g) is pumped into a previously evacuated 2.0 L reaction vessel. The total pressure of the reaction system is 1.2 atm at equilibrium. What will be the total equilibrium pressure of the system if the volume of the reaction vessel is reduced to 1.0 L at constant temperature?
Greater than 1.2 atm but less than 2.4 atm
A 0.5 mol sample of He(g) and a 0.5 mol sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25°C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why?
He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.
A sample of an ideal gas is cooled from 50.0oC to 25.0oC in a sealed container of constant volume. Which of the following values for the gas will decrease? I. The average molecular mass of the gas II. The average distance between the molecules III. The average speed of the molecules
III only
Equal masses of three different ideal gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct?
It depends on the relative molecular masses of X, Y, and Z.
Which of the following best helps explain why the pressure of a sample of CH4(�) (molar mass 16g/mol) is closer to the pressure predicted by the ideal gas law than a sample of NH3(�) (molar mass 17g/mol) ?
NH3 molecules are polar while CH4 molecules are not, and the greater attractions between NH3 molecules cause the molecules to collide with the walls of the container with less force.
The diagrams above represent two samples of Xe gas in containers of equal volume at 280K. Which of the following correctly compares the two samples in terms of their deviation from ideal gas behavior and explains why?
The gas in sample 2 would deviate more from ideal behavior because the Xe atoms are closer together, leading to an increase in intermolecular attractions.
A student is given two 10g samples, each a mixture of only NaCl(�) and KCl(�) but in different proportions. Which of the following pieces of information could be used to determine which mixture has the higher proportion of KCl(�) ?
The mass of Cl in each mixture
A 5.0g sample of MgCl2 may contain measurable amounts of other compounds as impurities. Which of the following quantities is (are) needed to determine that the sample is pure MgCl2 ?
The mass of Mg and the mass of Cl in the sample
Diagram 1 above shows equimolar samples of two gases inside a container fitted with a removable barrier placed so that each gas occupies the same volume. The barrier is carefully removed as the temperature is held constant. Diagram 2 above shows the gases soon after the barrier is removed. Which statement describes the changes to the initial pressure of each gas and the final partial pressure of each gas in the mixture and also indicates the final total pressure?
The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases
Ar(�) deviates more from ideal behavior at extremely high pressures than Ne(�) does. Which of the following is one reason for this difference?
The particle volume of Ar is greater than that of Ne.
When a sample of oxygen gas in a closed container of constant volume is heated until its absolute temperature is doubled, which of the following is also doubled?
The pressure of the gas
The reaction between NO(g) and O2(g) to produce NO2(g) in a rigid reaction vessel is represented in the diagram above. The pressure inside the container is recorded using a pressure gauge. Which of the following statements correctly predicts the change in pressure as the reaction goes to completion at constant temperature, and provides the correct explanation?
The pressure will decrease because there are fewer molecules of product than of reactants.
Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas
are relatively far apart
At standard temperature and pressure, a 0.50 mol sample of H2 gas and a separate 1.0 mol sample of O2 gas have the same
average molecular kinetic energy
Which flask contains the smallest number of moles of gas?
b) 50 and 20
The density of the gas, in g/L, is
greater in container B
The density of the gas, in g/L, is
greatest in container C
The gas particles in vessel 3 at 27°C are represented in the diagram above. The lengths of the arrows represent the speeds of the particles. Which of the following diagrams best represents the particles when vessel 3 is heated to 127°C?
the first one A
The average kinetic energy of the gas molecules is
the same in all 3 containers