AP Chemistry Test 1 - GASES
List the units of pressure and the numbers coordinated with them.
- 1 atm - 101.3 kPa - 760 mm Hg - 760 Torr
When do ideal gases deviate from ideal behaviour?
- High pressure - Low temperature
A manometer has a higher mercury level on the gas pressure side, (bubble/rounded), the gas pressure is 87.1 kPa, and the height is 155 mm Hg. Solve for X mm Hg.
Pgas = Patm - h x = 808 mm Hg
A manometer has a higher mercury level on the gas pressure side, (bubble/rounded), the atmospheric pressure is 1.25 atm, and the height is 510 mm Hg. Solve for X kPa.
Pgas = Patm - h x = 59 kPa
In measuring pressure of gas with a manometer, what must each unit be measured in?
Pressure has to all be in the same units Height = mm
An unknown gas is composed of homonuclear diatomic molecules, diffuses at a rate that is only 0.355 times that of O2 at the same temperature. Calculate the molar mass of the unknown and identify it.
Rate 1 = 0.355 x Rate 2 O2 = Rate 2 r1/r2 = __/MM2/MM1 R2 cancels out Swap MM1 and 0.355^2 MM1 = 253.92 g/mol I2 is the compound
Convert the following units : 1. 0.357 atm to Torr 2. 6.6 x 10^-2 Torr to atm 3. 147.2 kPa to Torr
1. 271 Torr 2. 8.7 x 10^-5 atm 3. 1104 Torr
If the volume doubles, the pressure ___.
1/2 - halves
If the pressure triples, the volume ___.
1/3 - thirds
If the volume goes down to a third, the temperature ___.
1/3 - thirds
The volume of a gas is tripled while the temperature is held constant. How does the gas pressure change?
1/3 - thirds
Average KE per mole = ___.
3/2 • RT
What is the average kinetic energy per mole of molecules for any gaseous system at STP?
3/2 •RT 3/2 • (8.314)(273) =3404.583 J/mol =3.404583 kJ/mol
With energy, R = ___ With volume, R = ___
8.314 0.0821
What determines what gases will haves higher rate of effusion?
A smaller molar mass
Which gas from each set will have the highest rate of effusion through a pinhole? A) Cl2 or F2 B) Xe or Kr C) N2 or O2 D) Cl2 or Ar E) 14C(g) or 12C(g) F) 1H(g) or 2H(g) G) 3He or 4He
A) F2 B) Xe C) N2 D) Ar E) 12C(g) F) 1H(g) G) 3He
A study of the effects of certain gases on plant growth requires a synthetic atmosphere composed of 1.5 mol CO2, 18.0 mol O2, and 80.5 mol Ar. A) Calculate the partial pressure of O2 in the mixture if the total pressure of the atmosphere is to be 745 Torr. B) If this atmosphere is to be held in a 121-L space at 295 K, how many moles of O2 are needed?
A) P(gas) = X(gas) = P(total) X(gas) = 18.0 mol/1.50+18.0+80.5 = 0.18 P(gas) = X(gas) • P(total) P(gas) = 134 Torr B) Convert Torr to atm PV = nRT n(O2) = 0.881 mol O2
A sample of KClO3 is partially decomposed producing O2 gas that is collected over water. The volume of gas collected is 0.250-L at 26.0*C and 765 Torr total pressure. A) How many moles of oxygen are collected? B) How many grams of KClO3 were decomposed?
A) P(total) = P(gas) + P(w.v.) Convert answer to atm P(gas)V = n(gas)RT N(O2) = 9.91 x 10^-3 mol B) 0.810 g
A 8.5-L tank contains Helium gas at 16.9 atm and 25*C. A) How many moles of He are available for making balloons? B) If all the Helium was used to fill 1.5-L red balloons at 0.99 atm and 32*C, how many balloons will you end up with?
A) PV = nRT n = 5.9 moles B) PV = nRT V = answer/1.5-L V = 99 balloons
The average velocity of a diatomic gaseous molecule is found to be 515 m/s at 25*C. A) What is the molar mass of the molecule? B) What is the identity of the molecule (gaseous)?
A) Urms = __/3RT/MM Square to get rid of square root Swap MM and Urms MM = 0.02802 kg/mol MM = 28.02 g/mol B) N2
To find Kelvin from Celsius, you do what?
Add 273 to the temperature
In any equation with "R", pressure must be in ___.
Atm
What is the density of carbon tetrachloride vapour at 714 torr and 125*C?
CCl4 = MM of 153.81g Torr to atm MM = dRT/P Cross multiply and divide d = 4.42 g/L
The following reaction goes to completion in a 6.3-L vessel at 78*C. H2 (g) + Cl2 (g) -> 2 HCl (g) The vessel contained 2.50 mol H2 and 1.00 mol Cl2 before the reaction took place. A) Find the mole fraction of all gases present after the reaction is complete. B) Find the total pressure in the vessel after the reaction C) Find the partial pressure of H2 after the reaction
Create I.C.E. Chart A) H2 = 1.50 mol/1.50 mol + 2.00 mol = 0.429 HCl = 2.00 mol/ 1.50 mol + 2.00 mol = 0.571 B) PV = nRT P(total)V = n(total)RT P(Total) = 16 atm C) PV = nRT P(H2) = n(H2)RT P(H2) = 6.9 atm
An unknown gas is collected in an 850.0-mL vessel at 1.02 atm and 23*C. The evacuated vessel has a mass of 138.45 grams and the vessel and gas have a combined mass of 140.12 grams. Find the molar mass of the gas.
D = m/v MM = dRT/P MM = 47 g/mol
What happens to the pressure of a gas inside a container if the temperature of the gas decreases?
Decreases
What happens to the temperature of a gas when it is compressed?
Decreases
In Avogadro's Law, it relates n and V, which are ___.
Directly proportional
In Charles' Law, it relates T and V, which are ___.
Directly proportional
In Gay-Lussac's Law, it relates P and T, which are ___.
Directly proportional
As the Kelvin temperature of the gas in a balloon doubles, what happens to the pressure?
Doubles
If the temperature (K) of gas doubles, the pressure of the gas.
Doubles
If the temperature doubles, the volume ___.
Doubles
If the volume of a container of air is reduced by one half, what happens to the partial pressure of oxygen within the container?
Doubles
A gaseous mixture made from 6.00 grams of O2 and 9.00 grams of CH4 is placed in a 15.0-L vessel at 0*C. What is the partial pressure of each gas, and what is the total pressure in the vessel? Solve in two different formulas.
Formula 1 Mole - mass conversion PV=nRT P(O2) = 0.28016625 atm Mole - mass conversion PV=nRT P(CH4) = 0.837880373 atm P(T) = P1 + P2 + .... P(T) = 1.12 atm Formula 2 Mole - mass conversion Mole - mass conversion P(total)V = n(total)RT P(T) = 1.12 atm
As the temperature of a fixed volume of gas increases, the pressure will ___.
Increase
Average velocity ___ as mass decreases.
Increases
If a balloon is heated, what happens to the pressure of the air inside the balloon if the volume remains constant?
Increases
If the volume of a container of gas is reduced, what will happen to the pressure inside the container?
Increases
In Boyle's Law, it relates P and V, which are ___.
Indirectly proportional
Calculate the rms speed, u, of a N2 molecule at 25*C.
MM Convert from g/mol to kg/mol by dividing by 1000 Urms = __/3RT/MM Urms = 515 m/s
What volume of CO2 (g) can be produced when 68 grams of propane, C3H8, burns in air at 25*C and 1.02 atm? C3H8 (g) + 5 O2 (g) -> 3 CO2 (g) + 4 H2O (l)
Mole - mass conversion PV = nRT VCO2 = 110-L or 1.1 x 10^2-L
To convert centimeters to milimeters, you must ___.
Multiply the centimeters by 10
Suppose you have two identical 1.0-L sealed containers. Both containers are kept at exactly 25*C. One vessel contains only neon gas at 1.5 atm, and the other contains only xenon gas at 1.9 atm. Is the value for the moles of neon less than, equal to or greater than that of xenon. Explain.
Neon : PV = nRT n = 0.061 moles Xenon : PV = nRT n = 0.078 moles The value for the moles of neon is less than that of xenon. This is because xenon had a higher pressure, which is directly proportional to the moles, so the moles increased too.
The Combined Gas Law is :
P1 x V1/T1 = P2 x V2/T2
An inflated balloon had a volume of 6.0-L at sea level (1.0 atm) and is allowed to ascend to an altitude until the pressure is 0.45 atm. During the ascent the temperature of the gas falls from 22*C to -21*C. Calculate the volume of the balloon at its final altitude.
P1 x V1/T1 = P2 x V2/T2 Cross multiply and divide V2 = 11-L
A gas left in a used aerosol can is at a pressure of 100. kPa at 27*C. If this can is thrown onto a fire, what is the internal pressure of the gas when its temperature reaches 927*C?
P1/T1 = P2/T2 Cross multiply and divide P2 = 400 kPa
A balloon is filled with 30.-L of helium gas at 100. kPa. What is the volume when the balloon rises to an altitude where the pressure is only 25 kPa?
P1xV1 = P2xV2 V2 = 120-L
The Ideal Gas Equation is :
PV = nRT
If an air bag has a volume of 36-L and is to be filled with nitrogen gas at a pressure of 1.15 atm at a temperature of 26.0*C, how many grams of NaN3 must be decomposed?
PV = nRT Mole - mass conversion = 73 g NaN3
The equation of a manometer with a liquid at equal levels on both sides is ___.
Pgas = Patm
A manometer has an equal mercury level, the atmospheric pressure is 75.2 kPa, and the height is 0 mm Hg. Solve for X mm Hg.
Pgas = Patm x = 564 mm Hg
A manometer has a higher mercury level on the atmospheric pressure side, (long skinny tube), the atmospheric pressure is 115.4 kPa, and the height is 623 mm Hg. Solve for X atm.
Pgas = Patm + h
The equation of a manometer with a liquid higher on the atmospheric pressure side, (long skinny tube), is ___.
Pgas = Patm + h
A manometer has a higher mercury level on the atmospheric pressure side, the gas pressure is 135.5 kPa, and the height of the water is 208 mm Hg. Solve for X atm.
Pgas = Patm + h x = 1.06 atm
A manometer has a higher mercury level on the atmospheric pressure side, (long skinny tube), the atmospheric pressure is 1.42 atm, and the height is 465 mm Hg. Solve for X kPa.
Pgas = Patm + h x = 206 kPa
The equation of a manometer with a liquid higher on the gas pressure side, (bubble/round), is ___.
Pgas = Patm - h
What values should you not use for figs?
STP : 0*C, 273 K, 101.3 kPa, 1 atm
What is STP?
Standard temperature (0*C) and pressure (101.3 kPa / 1 atm)
If a gas is heated to triple its Kelvin temperature, what happens to the pressure of the gas?
Triples
A balloon inflated in an air-conditioned room at 27*C, has a volume of 4.0-L. It is heated to a temperature of 57*C. What is the new volume of the balloon if the pressure remains constant?
V1/T1 = V2/T2 V2 = 4.4-L
What is the formula for Avagadro's Law?
V1/n1 = V2/n2
g/mol = ___
g • mol^-1
MM must be measured in ___ in Urms problems.
kg/mol
m/s = ___
m • s^-1
Speed = ___
m/s
