Properties of all gases

Chapter 14

with Ch 13 review.

WOD are underlined.

Properties of all gases• When working with gases, there are 4 properties that must

be considered:

Gas Properties: Mass, Volume, Pressure, Temperature

• There are multiple equations: The properties that change determine the equation to select to solve for the unknown.

• All the remaining properties must be held constant.

From Chapter 13

Phases

• Two of the properties determine the phase of an element:

• Pressure

• Temperature

From Chapter 13

Phases

• What happens when you increase pressure (a lot) on gas?

(What is one exception?)

• What happens when you increase temperature (a lot) on a solid?

There is a pan of ice on the stove.

What does this Temperature graph

look like?

WRONG!

Properties of all gasesKNOW ALL THE FOLLOWING:

• Pressure at STP is:– 1 atm = 760 mm Hg = 101.3 kPa = 14.7 lbs/in2

• Volume– 1 mL = 0.001L = 1cm3

• Temperature at STP is 273 K (0° Celsius)– Use Kelvin (not Celsius)

Standard Temperature and Pressure:STP, Temperature and Pressure at Sea Level

on a freezing day = 101.3 kPa, 273 K

KNOW ALL THE FOLLOWING:• Pressure at STP is:

– 1 atm = 760 mm Hg = 101.3 kPa = 14.7 lbs/in2

• Volume– 1 mL = 0.001L = 1cm3

• Temperature at STP is 273 K (0° Celsius)– Use Kelvin (not Celsius)

Properties of all gases

• Pressure– 1 atm = 760 mm Hg = 101.3 kPa = 14.7 lbs/in2

Discuss Gage pressure in a factory (diff from atm. Vs gage pressure in a lab (Boyles Law)

Boyle’s Law – what happens to pressure?

Boyle’s Law P1V1 = P2V2

(mass and temperature constant) Volume of a gas varies inversely

with pressure V↑P↓ or P↑V↓P1V1 = P2V2

Or PV = Constant

Steps to Solve Problems:1. Known: Find the knowns.

2. Unknown: Find the unknowns.3. Equation: Pick the equation that matches the knowns and unknowns.

4. Units: Make sure units are the same on both sides. T in Kelvin.

5. SigFig: Change the answer to the correct number of significant

figures.

A 220mL balloon of air is at a pressure of 506.5kPa. What will be the volume of the balloon at

sea level (STP)?

A 455mL balloon is taken from sea level up to a point where the

pressure is unknown. The balloon has a new volume of 1.25L. What

is the pressure?

Review the last 2 slides. As height goes up:

What happens to pressure?What happens to volume?

NaHCO3 + HC2H3O2 H2O +NaC2H3O2 + CO2

At STP, 2.5g of NaHCO3 produced 560 mL of CO2 gas. What would the volume of this

gas be on top of mountain where the pressure is only 250 mm Hg?

Extra credit – What is the percent yield of CO2 produced? (Use Mass ratio’s)

NaHCO3 + HC2H3O2 H2O +NaC2H3O2 + CO2

At STP, 2.5g of NaHCO3 yields 560 mL of CO2 P2 = 250 mm Hg?

Extra credit – What is the percent yield of CO2 produced?

Charles’s Law – What happens to a gas if it is heated?

Charles’s Law V1/T1=V2/T2

(mass and pressure constant)

Volume of a gas varies directly with its Kelvin temperature

T↑ V↑ or T↓V↓V1/T1=V2/T2

or V/T = Constant

A balloon is filled with 5.00L of air with a temperature of 00C.

The balloon is placed by a furnace and expands to 7.00L. What is the temperature next to

the furnace? Hint: Use 273K

Gay-Lussac’s Law P1/T1=P2/T2

(mass and volume constant) pressure of a gas varies directly with

its Kelvin temperature P↑ T↑ or P↓T↓

P1/T1=P2/T2

or P/T=Constant

Combined Gas Law:(Temp is in Kelvin)

The volume of a “Get Well Soon” balloon is 2.5L at STP conditions. What would the volume of the balloon be on the moon (-930C, 1.1x10-8kPa)

Quiz 14.2A can of compressed air ruptures

at an internal pressure of 225 lbs/in2. At standard temperature

(0.00oC) the pressure is 55.5 lbs/in2. At what temperature will the can burst (reach it bursting

pressure)?

Ideal Gas LawPV=nRT

Prairie Village is not a Real Town R= 8.31 ( L•kPa)/(K •mol)

P, V, Tn = moles

R= 8.31 ( L•kPa)/(K •mol)

How many grams of He are needed to fill a weather balloon that is 2520L at

sea level and 5.75oC?

What is the pressure on the inside of a CO2 cartridge?

(There are 12.1 grams, the temperature in the room is 68.7F, and the volume is 15.9mL.)

Would the pressure change if the room temperature changed?

PV=nRTX (0.0159L) = 0.275mol (8.31 L .kPa/mol.K) 293.4K

42,200 kPa or 42,169.33019 kPaabout 417atm

Sample Problem

NaHCO3 + HC2H3O2 H2O +NaC2H3O2 + CO2

A classroom has a temperature of 303K and a pressure of 105kPa. What volume of CO2 will be produced from

12.5g of NaHCO3?

Quiz 14.3 How many moles of H2 are needed to

fill a balloon that is 2.50L, at sea level, and 295.75K?

Extra credit –H2O + Na NaOH + H2

How many grams of Na will it take to fill the balloon?

Review

Properties of all gases• When working with gases, there are 4 properties that must

be considered:

Gas Properties: Mass, Volume, Pressure, Temperature

• There are multiple equations: The properties that change determine the equation to select to solve for the unknown.

• All the remaining properties must be held constant.

Properties of all gasesKNOW ALL THE FOLLOWING:

• Pressure at STP is:– 1 atm = 760 mm Hg = 101.3 kPa = 14.7 lbs/in2

• Volume– 1 mL = 0.001L = 1cm3

• Temperature at STP is 273 K (0° Celsius)– Use Kelvin (not Celsius)

Combined Gas Law:(Temp is in Kelvin)

Ideal Gas LawPV=nRT

Prairie Village is not a Real Town R= 8.31 ( L•kPa)/(K •mol)

P, V, Tn = moles

R= 8.31 ( L•kPa)/(K •mol)

Steps:1. Known: Find the knowns.

2. Unknown: Find the unknowns.3. Equation: Pick the equation that matches the knowns and unknowns.

4. Units: Make sure units are the same on both sides. T in Kelvin.

5. SigFig: Change the answer to the correct number of significant

figures.