10.2 Mole-Mass and Mole- Volume Relationshipskdteel.weebly.com/uploads/4/9/7/0/4970193/chapter_10_ppt2.pdf · 10.2 Mole-Mass and Mole-Volume Relationships . 10.3 Percent Composition

10.2 Mole-Mass and Mole- Volume Relationships

1

>

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Chapter 10 Chemical Quantities 10.1 The Mole: A Measurement of

Matter 10.2 Mole-Mass and Mole-

Volume Relationships 10.3 Percent Composition and

Chemical Formulas


2

>

http://www.brightstorm.com/science/chemistry/chemical-reactions/molar-mass/


http://www.brightstorm.com/science/chemistry/chemical-reactions/molar-mass/�

http://www.brightstorm.com/science/chemistry/chemical-reactions/molar-mass/�


3

>


How can you calculate the moles of a substance in a given mass or volume?

CHEMISTRY & YOU

Guess how many pennies are in the container. In a similar way, chemists use the relationships between the mole and quantities such as mass, volume, and number of particles to solve problems in chemistry.


4

>


The Mole-Mass Relationship

How do you convert the mass of a substance to the number of moles of the substance?



5

>


Use the molar mass of an element or compound to convert between the mass of a substance and the moles of the substance.



6

>



molar mass 1 mol

1 mol molar mass

and


• The conversion factors for these calculations are based on the relationship molar mass = 1 mol.


7

>


Items made out of aluminum, such as aircraft parts and cookware, are resistant to corrosion because the aluminum reacts with oxygen in the air to form a coating of aluminum oxide (Al2O3). This tough, resistant coating prevents any further corrosion. What is the mass, in grams, of 9.45 mol of aluminum oxide?

Sample Problem 10.5

Converting Moles to Mass


8

>


The mass of the compound is calculated from the known number of moles of the compound. The desired conversion is moles → mass.

KNOWN number of moles = 9.45 mol Al2O3 UNKNOWN mass = ? g Al2O3

Sample Problem 10.5

Analyze List the known and the unknown. 1


9

>


First determine the mass of 1 mol of Al2O3.

Sample Problem 10.5

Calculate Solve for the unknown. 2

2 mol Al × = 54.0 g Al

3 mol O × = 48.0 g O

1 mol Al2O3 = 54.0 g Al + 48.0 g O = 102.0 g Al2O3

27.0 g Al 1 mol Al 16.0 g O 1 mol O


10

>


Identify the conversion factor relating moles of Al2O3 to grams of Al2O3.

1 mol Al2O3 102.0 g Al2O3 Use the relationship

1 mol Al2O3 = 102.0 g Al2O3.

Sample Problem 10.5



11

>


Multiply the given number of moles by the conversion factor.

Sample Problem 10.5


9.45 mol Al2O3 × 102.0 g Al2O3

1 mol Al2O3

= 964 g Al2O3


12

>


When iron is exposed to air, it corrodes to form a red-brown rust. Rust is iron(III) oxide (Fe2O3). How many moles of iron(III) oxide are contained in 92.2 g of pure Fe2O3?

Converting Mass to Moles

Sample Problem 10.6


13

>


The Mole-Volume Relationship

How do you convert the volume of a gas at STP to the number of moles of the gas?



14

>


Notice that the volumes of one mole of different solid and liquid substances are not the same.


• The volumes of one mole of glucose (blood sugar) and one mole of parachlorobenzene (moth crystals) are much larger than the volume of one mole of liquid water.


15

>


Unlike liquids and solids, the volumes of moles of gases, measured under the same physical conditions, are much more predictable.



16

>


Avogadro’s hypothesis states that equal volumes of gases at the same temperature and pressure contain equal numbers of particles.


Avogadro’s Hypothesis


17

>


The particles that make up different gases are not the same size.


• However, particles in all gases are so far apart that a collection of relatively large particles does not require much more space than the same number of relatively small particles.



18

>


Whether the particles are large or small, large expanses of space exist between individual particles of gas.




19

>


The volume of a gas varies with a change in temperature or a change in pressure.




20

>





• Due to these variations with temperature and pressure, the volume of a gas is usually measured at standard temperature and pressure.


21

>





• Due to these variations with temperature and pressure, the volume of a gas is usually measured at standard temperature and pressure.

• Standard temperature and pressure (STP) means a temperature of 0°C and a pressure of 101.3 kPa, or 1 atmosphere (atm).


22

>


At STP, 1 mol, or 6.02 × 1023 representative particles, of any gas occupies a volume of 22.4 L.

• The quantity, 22.4 L, is called the molar volume of a gas.




23

>


The molar volume is used to convert between the number of moles of gas and the volume of the gas at STP.

Calculating the Volume and Moles of a Gas at STP

22.4 L 1 mol

1 mol 22.4 L

and


• The conversion factors for these calculations are based on the relationship 22.4 L = 1 mol at STP.


24

>


• You can use these conversion factors to convert a known number of moles of gas to the volume of the gas at STP.

• Similarly, you can convert a known volume of gas at STP to the number of moles of the gas.


Calculating the Volume and Moles of a Gas at STP

22.4 L 1 mol

1 mol 22.4 L

and


25

>


Sulfur dioxide (SO2) is a gas produced by burning coal. It is an air pollutant and one of the causes of acid rain. Determine the volume, in liters, of 0.60 mol SO2 gas at STP.

Sample Problem 10.7

Calculating Gas Quantities at STP


26

>


Since SO2 is a gas, the volume at STP can be calculated from the known number of moles.

KNOWNS number of moles = 0.60 mol SO2 1 mol SO2 = 22.4 L SO2 at STP UNKNOWN volume = ? L SO2

Sample Problem 10.7

Analyze List the knowns and the unknown. 1


27

>


First identify the conversion factor relating moles of SO2 to volume of SO2 at STP.

22.4 L SO2 1 mol SO2

The following relationship applies for gases at STP: 22.4 L = 1 mol.

Sample Problem 10.7



28

>


Multiply the given number of moles by the conversion factor.

Sample Problem 10.7


0.60 mol SO2 × 22.4 L SO2 1 mol SO2

= 13 L SO2


29

>


• One mole of any gas at STP has a volume of 22.4 L, so 0.60 mol should have a volume slightly larger than one-half of a mole or 11.2 L.

• The answer should have two significant figures.

Sample Problem 10.7

Evaluate Does the result make sense? 3


30

>


How can you calculate the moles of a substance in a given mass? How can you calculate the moles of a gas in a given volume at STP?

CHEMISTRY & YOU


31

>


How can you calculate the moles of a substance in a given mass? How can you calculate the moles of a gas in a given volume at STP? You can calculate the moles of a substance in a given mass by using the relationship molar mass = 1 mol. You can calculate the moles of gas in a given volume at STP by using the relationship 22.4 L = 1 mol at STP.

CHEMISTRY & YOU


32

>


A gas-filled air balloon will either sink or float in the air depending on whether the density of the gas inside the balloon is greater or less than the density of the surrounding air.

Calculating Molar Mass and Density


• Different gases have different densities.

• Usually the density of a gas is measured in grams per liter (g/L) and at a specific temperature.


33

>


• The density of a gas at STP and the molar volume at STP (22.4 L/mol) can be used to calculate the molar mass of the gas.

• Similarly, the molar mass of a gas and the molar volume at STP can be used to calculate the density of a gas at STP.


Calculating Molar Mass and Density


34

>


The density of a gaseous compound containing carbon and oxygen is found to be 1.964 g/L at STP. What is the molar mass of the compound?

Sample Problem 10.8

Calculating the Molar Mass of a Gas at STP


35

>


The molar mass of the compound is calculated from the known density of the compound and the molar volume at STP.

KNOWNS density = 1.964 g/L 1 mol of gas at STP = 22.4 L UNKNOWN molar mass = ? g/mol

Sample Problem 10.8

Analyze List the knowns and the unknown. 1


36

>


Sample Problem 10.8

First identify the conversion factor needed to convert density to molar mass.

22.4 L 1 mol

Use the density and molar volume at STP to calculate the molar mass.

molar mass = g

mol = g L ×

22.4 L 1 mol



37

>


Multiply the given density by the conversion factor.

Sample Problem 10.8


= 44.0 g/mol

1.964 g 1 L

22.4 L 1 mol ×


38

>


• The ratio of the calculated mass (44.0 g) to the volume (22.4 L) is about 2, which is close to the known density.

• The answer should have three significant figures.

Sample Problem 10.8

Evaluate Does the result make sense? 3


39

>


The mole is at the center of your chemical calculations.


• To convert from one unit to another, you must use the mole as an intermediate step.


40

>


Why does one mole of any gas occupy the same volume (22.4 L) at standard temperature and pressure?


41

>


Why does one mole of any gas occupy the same volume (22.4 L) at standard temperature and pressure?

Gas molecules do vary in size, just like molecules of solids and liquids, but the particles in a gas are always so far apart that the change in volume of the molecules doesn’t change the volume the gas occupies at STP.


42

>



The molar volume is used to convert between the number of moles of gas and the volume of the gas at STP.

Key Concepts


43

>


• Avogadro’s hypothesis: equal volumes of gases at the same temperature and pressure contain equal numbers of particles

• standard temperature and pressure (STP): the conditions under which the volume of a gas is usually measured; standard temperature is 0°C, and standard pressure is 101.3 kPa, or 1 atmosphere (atm)

• molar volume: the volume occupied by 1 mole of a gas at standard temperature and pressure (STP); 22.4 L

Glossary Terms


44

>


The mole allows you to convert among the amount of representative particles in a substance, the mass of a substance, and the volume of a gas at STP.

BIG IDEA

The Mole and Quantifying Matter

Documents

10.2 Mole-Mass and Mole- Volume Relationshipskdteel.weebly.com/uploads/4/9/7/0/4970193/chapter_10_ppt2.pdf · 10.2 Mole-Mass and Mole-Volume Relationships . 10.3 Percent Composition