Gases - Chemistry
If a gas remains at standard pressure and its temperature is slowly increased, which of the following is true about the volume of the gas?
According to Charles' Law, the volume and temperature of a gas are directly proportional if the pressure is constant.
In a gaseous mixture, two particles collide. Kinetic energy before the collision is the same as kinetic energy after the collision. Which assumption of the kinetic molecular theory of gases best explains this behavior?
All of these assumptions are necessary to apply the kinetic molecular theory of gases. However, elastic collisions best explains the conservation of kinetic energy that is described in the question.
The temperature of a gaseous mixture is increased by 2 oC. Which of the following will happen in the mixture?
Increasing the temperature of a gas increases the average velocity of the gas particles, but not necessarily the velocity of each individual particle.
Boyle's Law
P1V1=P2V2 A principle that describes the relationship between the pressure and volume of a gas at constant temperature
A gas sample at 600.0 K and 3.0 atm is compressed until the volume is halved. The gas is then cooled, causing the temperature to decrease to 400.0 K. What is the final pressure of the gas sample?
The combined gas law is P1V1/T1 = P2V2/T2. Rearrange to solve for the final pressure, P2. P2 = P1V1T2/T1V2 P2 = (3.0 atm)(1 L)(400.0 K) / (600.0 K)(0.5 L) P2 = 4.0 atm
Best describes the particle of ideal gas, based on the kinetic molecular theory?
The gas particles have no attractive forces between them.
A 10-liter sample of CO gas contains the same number of molecules as how many liters of O gas at the same temperature and pressure?
The number of molecules in a 10-liter sample of CO gas is 2.69x10^23 molecules, and the number of molecules in a 10 lifter sample of O gas is also 2.69x10^23 molecules. So the answer would be 10 liters.
A gaseous mixture with a total pressure of 5 atm is composed of 10% N2, 20% He, 30% H2O, 40% CO2. Which represents the combined partial pressures of N2 and He?
The partial pressure of a subset of components is the sum of the pressures of each individual component. Nitrogen and helium make up 30% of the gas mixture, so the partial pressure is 1.5 atm or 3/2 atm.
When the volume decreases in a sample of ideal gas molecules in a closed container of constant temperature, which of the following changes occurs?
This is Boyle's law. For a sample of gas molecules in a closed container, when temperature is constant and pressure increases, the volume of the gas sample will decrease. When the volume decreases, the molecules become more tightly packed, colliding more with each other and the container. The result is an increase in pressure.
Ideal Gas Law
the relationship PV=nRT, which describes the behavior of an ideal gas
A sample of gas confined in a cylinder with a moveable piston is kept at a constant pressure. The volume of the gas is doubled when the temperature of the gas is changed from
200k-400k always measured in kelvins.
Excess HCl is added to 234 g of Na2S solution as shown by the equation below: Na2S(aq) + 2HCl(aq) →2NaCl(aq) + H2S(g) How many liters of H2S gas are produced at standard temperature and pressure (STP)? The molar mass of Na2S is 78 g.
234 g of Na2S is 3 moles, therefore 3 moles of H2S are produced. The volume of one mole of an ideal gas at STP is 22.4 L. Therefore the volume of H2S gas produced is 3 × 22.4 L = 67.2 L.
A 600 L canister of helium gas is held at a pressure of 0.987 atm and a temperature of 250 K. What is the pressure of the same gas if it is heated to 450 K?
According to the Combined Gas Law, P1V1 / T1 = P2V2 / T2. In this case, P1 = 0.987, V1 = 600, T1 = 250, V2 = 600, T2 = 450, and P2 is what we are looking for. Substituting into the Combined Gas Law equation gives 1.7766 atm, which can be rounded to 1.78 for the correct number of significant figures.
In a laboratory, 10 moles of HE gas (atomic mass of 4.0) were placed in a rigid 2-liter tank. The tank had a small pinhole leak and the He gas escpaed. If 10 moles of Ar gas (atomic mass 40 ) had been places instead in the tank at the same temperature, predict how the Ar would have leaked out compared to the He.
Argon atoms have larger masses. Therefore, Ar will move slower.
Best explains why the pressure inside a high flying airplane muse be controlled?
At high altitudes there is lower atmospheric pressure than on the surface of the Earth. - The higher you go the less the air pressure become.
A sample of two moles of an ideal gas with constant temperature has an initial pressure of 2.0 atm and an initial volume of 2.0 L. If the pressure is increased to 3.0 atm, which of the following is true about the volume of the gas sample?
Based on the ideal gas law, pressure and volume are inversely related. At constant temperature, the volume will decrease if the pressure is increased. If 2.0 mol of a gas has an initial volume of 2.0 L and pressure of 2.0 atm, when the pressure increases to 3.0 atm, the volume will decrease proportionally.
A gas sample is at 25C and 1 atmosphere. Which changes in temperature and pressure will cause this samples to behave more like an ideal gas?
Increasing temperature and decreased pressure. Gas behave more like ideal gasses when the temperature is higher and the pressure is lower.
A sample of nitrogen, N2, occupies 55.0 mL at 300 K and 1.0 atm. What pressure will it have if cooled to 200 K while the volume remains constant?
Pressure is directly proportional to the absolute temperature when the volume is constant. Therefore P1/T1 = P2/T2. 1.0 atm/300 K = P2/ 200K. P2 = 0.7 atm.
Which of the following accounts for the pressure a gas exerts?
The constant movement of gas molecules means they are constantly colliding with the container walls, which accounts for the pressure the gas exerts.
The pressure of an ideal gas is doubled as its volume is decreased to one-third of the original volume. What happens to the temperature during this process?
The ideal gas law states that the product of pressure P and volume V equals the product of the number of moles n, the gas constant R, and the temperature T: PV = nRT. Inserting 2P and V/3 for pressure and volume indicates the temperature must decrease by a factor of ⅔ since n and R remain constant: 2P(V/3) = nR(2T/3).
Which of the following would be the best classroom demonstration of Boyle's law?
The marshmallow demonstration will clearly show the inverse relationship between pressure and volume as described by Boyle's law. Additionally, the temperature of the marshmallow will remain relatively constant.
A gaseous mixture is made up of 0.2 Mol/L H2O, 0.3 Mol/L Ar, and 0.5 Mol/L N2. If the mixture is in a 10 L container with a temperature of 250 K, what pressure does the mixture exert?
Use the ideal gas law PV = nRT to find the total pressure of the mixture. Substitute in values: V = 10 L, T = 250 K, and n = (.2 M + .3 M + .5M) ᐧ 10 L = 10 mol of gas. Solve for P for a final equation of P = 10 mol(R)(250 K)/ 10 L.
Charles Law
V1/T1=V2/T2 the law that states that for a fixed amount of gas at a constant pressure, the volume of the gas increases as the temperature of the gas increases and the volume of the gas decreases as the temperature of the gas decreases
How does the temperature of a sample of an ideal gas change when its pressure decreases to half its original value and its volume increases to 3 times its original volume?
rom the ideal gas law: \frac{P_{1}V_{1}}{T_{1}}=\frac{P_{2}V_{2}}{T_{2}}T1P1V1=T2P2V2. Substitute the given proportions (P2 = ½ P1 and V2 = 3V1 ) into the ideal gas law relationship above. Let X equal the final temperature, cancel like terms, and solve. \frac{P_{1}V_{1}}{T_{1}}=\frac{ \left( \frac{1}{2}P_{1} \right) \left( 3V_{1} \right) }{X}T1P1V1=X(21P1)(3V1) X = \frac{3}{2}T_{1}X=23T1 Therefore, the temperature increases to 3/2 of its original value.
