Gases Unit Review
A sample of helium gas in a balloon is compressed from 4.0 L to 2.5 L at a constant temperature. If the pressure of the gas in the 4.0-L volume is 210 kPa, what will the pressure be at 2.5 L?
(210 kPa)(4.0 L) = P2(2.5 L) P2 = 340 kPa (336 rounded to 2 s.f.)
A sample of chlorine gas occupies a volume of 946 mL at a pressure of 726 mmHg. What is the pressure of the gas if the volume is reduced to 154 mL?
(726 mmHg) (846 mL) = p2 (154ml) P2= 4460 mL
What Celsius temperature corresponds with absolute zero?
-273 C
A chemical reaction produces 0.068 mol of oxygen gas. What volume in liters is occupied by this gas sample at STP?
.068 mol x 22.4 L/ 1mol = 1.5 L
Calculate the volume that 0.881 mol of gas at standards temperature and pressure (STP) will occupy
.88 mol x 22.4L/mol= 19.7L
Write the conversion factor for Molar Volume
1 mol = 22.4 L
What conditions represent standard temperature & pressure (STP)?
1 tm, 0 degrees C
How many moles of nitrogen gas will be contained in a 2.00-L flask at STP?
2L x 1mol/22.4L=.0893
A sample of carbon monoxide gas occupies 3.20 L at 125 °C. At what temperature will the gas occupy a volume of 1.54 L if the pressure remains constant?
3.2L/398K= 1.54L/T2 T2(3.2L)= (1.54L) (398K) T2=192K
The Celsius temperature of a 3.00-L sample of gas is lowered from 80.0°C to 30.0°C. What will be the resulting volume of this gas?
3L/353K = V2/303K V2 (353K)= (3L) (303K) V2= 2.58 L
Normal atmospheric pressure at sea level is ______
760 mmHg
The volume of a gas at 99.0 kPa is 300.0 mL. If the pressure is increased to 188 kPa, what will be the new volume?
99.0 kPa)(300.0 mL) = (188 kPa)V2 V2 = 158 mL
Given the following reaction: C3H8(g) + 5 O2(g) → 3 CO2 + 4 H2O(g) If the intial rate of the reaction produces 2 moles of water vapor, H2O, per second, what is the rate at which propane, C3H8, is consumed initially? A. 0.5 moles per second B. 1 mole per second C. 2 moles per second D. 4 moles per second
A. 0.5 moles per second
In chemical reactions, electricity, a spark, and sunlight are all ways in which _______________ may be provided. A. activation energy B. reactants C. products D. catalysts
A. activation energy
How do gases exert pressure?
By colliding with objects in their path The sum of all the collisions make up the pressure the gas exerts
At 25 ºC, a certain reaction is able to produce 0.80 moles of product per minute? At what rate might the product be produced at 35 ºC? A. ? 0.80 moles per minute B. ? 0.20 moles per minute C. ? 1.6 moles per minute D. ? 0.40 moles per minute
C. ? 1.6 moles per minute
When N2 is removed from the following system at equilibrium: 3 H2(g) + N2(g) ⇌ 2 NH3(g) A. In order to restore equilibrium, the reaction shifts right, toward products B. No change occurs C. In order to restore equilibrium, the reaction shifts left, toward reactants
C. In order to restore equilibrium, the reaction shifts left, toward reactants
When the temperature is decreased on a closed system containing water and its vapor at equilibrium: H2O(l) + heat ⇌ H2O(g) A. In order to restore equilibrium, more liquid water evaporates B. No change occurs C. In order to restore equilibrium, water vapor condenses to form liquid water
C. In order to restore equilibrium, water vapor condenses to form liquid water
23. A child receives a balloon filled with 2.30 L of helium from a vendor at an amusement park. The temperature outside is 38C. What will be the volume of the balloon when the child brings it home to an air-conditioned house at 22C?
Charle's Law V2= V1T2/T1 (2.3L) (295K)/311K = 2.18L
A helium balloon with a volume of 410. mL is cooled from 27C to -27C. The pressure on the gas is reduced from 110. kPa to 25. kPa. What is the volume of the gas at the lower temperature and pressure?
Combined Gas Law V2= P1V1T2/P2T1 (110 kPa) (410 mL) (246L)/(25kPa) (300k) = 1500 mL
What is the Kinetic Molecular Theory
Gas molecules are small and spaced very far apart. gas molecules neither attract nor repel each other. gas molecules are in constant random motion. Gas molecules move in a straight path until they collide with either the wall of their container or another molecule. Gas molecules' collisions are elastic
What are some characteristics of gases?
Gases have mass. Gases assume the volume and shape of their containers. Gases have much lower densities than liquids and solids. Gases are compressible Gases expand to fill their containers. Gases diffuse Gases exert pressure
Which would behave more ideally C4H10 H2
H2 because it has a smaller molar mass
particles take up no space & have no intermolecular atrractive/repulsive forces
Ideal Gas
When the temperature is decreased on the following system at equilibrium: 2 HCl(aq) + Mg(s) ⇌ MgCl2(aq) + H2(g) + heat A. ? In order to restore equilibrium, the reaction shifts right, toward products B. ? In order to restore equilibrium, the reaction shifts left, toward reactants C. ? No change occurs
In order to restore equilibrium, the reaction shifts right, toward products
If temperature increases, the particles will have more kinetic energy and spread further apart, so volume ____
Increases
How do you convert Celsius temperature to Kelvin
Just add 273
Calculate the number of moles of gas contained in a 3.0-L vessel at 300 K with a pressure of 1.50 atm.
P = 1.50 atm V = 3.0 L n = ? T = 300 K Because the pressure is given in atm, we will use R = 0.0821 (L·atm/mol·K) (1.50 atm)(3.0 L)=n(0.0821l atm/mol k) (300K) n= .183 mol
Determine the Celsius temperature of 2.49 moles of gas contained in a 1.00-L vessel at a pressure of 143 kPa.
P = 143 kPa V = 1.00 L n = 2.49 mol T = ? R = 8.314 equation image indicator 143 kPa)(1.00 L)=(2.49 mol)(8.314 (t) T= 6.91K so subtract 273 T= -266 C
Write the equation for Combined Gas Law
P1V1/T1= P2V2/T2
What is the formula for Boyle's law
P1V1=P2V2
Write the equation for Boyle's Law
P1V1=P2V2
The equation for the ideal gas law is?
PV= nRT
Gases depend on temperature. T/F
T
Ideal gases take up no space, therefore small molecules behave more ideally. T/F
T
What is Boyle's law?
The pressure of a gas is inversely related to volume when temperature is held constant.
This is the aqueous iron(III) thiocyanate equilibrium: Fe3+(yellow) + SCN-(colorless) ⇌ [FeSCN]2+(dark red) If aqueous iron(III) chloride is added to the solution at equilibrium: A. ? The solution turns darker red B. ? The solution becomes colorless C. ? No change in color occurs D. ? The solution becomes more yellow
The solution turns darker red
What is Charle's Law?
The volume of a gas is directly related to Kelvin temperature when pressure is held constant.
What is the formula for Charles's Law?
V1/T1= V2/T2
Write the equation for Charle's Law
V1/T1=V2/T2
If volume decreases, there is less room for the molecules to move around so they will collide more, generating _____ pressure. a.higher b. lower
a higher
12.Which of the following will slow down the rate of a chemical reaction? a.Decreasing the temperature b.Increasing the pressure c.Addition of a catalyst d.Increasing the surface area of the reactants e.Increasing the concentration of reactants
a.Decreasing the temperature
14.Given the following reaction: Choose all that apply H2(g) + Cl2(g) → 2 HCl As this reaction takes place: a.HCl is produced at the same rate that H2 is consumed b.H2 and Cl2 are consumed at the same rate c.HCl is produced at the twice the rate that Cl2 is consumed d.HCl is produced at the half the rate that Cl2 is consumed
b.H2 and Cl2 are consumed at the same rate c.HCl is produced at the twice the rate that Cl2 is consumed
13.An increase in temperature increases the rate of a chemical reaction by what means. Choose all that apply. a.Increasing the concentration of reactants b.Increasing collision energy c.Decreasing activation energy d.Increasing pressure e.Increasing collision frequency
b.Increasing collision energy e.Increasing collision frequency
instrument used to measure pressure
barometer
Pressure is measured with an instrument called a ______
barometer.
According to Boyle's Law, as pressure increases, volume _______________.
decrease
As temperature goes down, volume _____
decreases
movement of particles from areas of high to low concentration
diffusion
as pressure of a gas goes up, the volume goes ___
down.
Gas particle collisions are __________, which means that energy is not lost.
elastic
describes collisions between gas molecules in which energy is conserved
elastic
state of matter with neither definite shape nor volume
gas
What does the R stand for in PV=nRT
gas constant If P is in atm, R = 0.0821 If P is in kPa, R = 8.314 If P is in mmHg or torr, R = 62.4
If volume of a gas decreases, pressure ______
increases
With polar molecules there are _____ and _____
intermolecular attractions and repulsions
temperature scale with absolute zero as its starting point
kelvin
temperature is a measure of average ___ energy
kinetic
Gases follow the __________ _______________ __________ which describes gases in terms of particle motion.
kinetic molecular theory
An important property of gases is that they consist of small particles spread far apart so that there are __________ attractive/repulsive forces
no
What are the 4 variables which can affect the behavior of gas molecules
number of particles (n) pressure (P) volume (V) temperature (T)
SI unit of pressure
pascal
The SI unit for pressure is ____
pascals (Pa)
defined as force per unit area
pressure
force per unit area
pressure
