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