1. Mole-Mass & Mole-Volume Relationships
Section 10.2
Mole-Mass & Mole-Volume Relationships

2. Last time we talked about..
What is a Mole?

3. Last time we talked about..
What is Avogadro’s number?

4. Last time we talked about..
What are representative particles?

5. Last time we talked about..NA
Count-Mole Relationship
Convert number of particles moles
Different definitions for masses
Gram atomic mass (gam)
looking at the mass of individual atoms eg. Fe, Mg
Gram molecular mass (gmm)
Looking at the mass of molecular compounds eg. CO2, N2, C3H8
Gram formula mass (gfm)
Looking at the mass of ionic compounds eg. NaCl, KBr

6. Last time we talked about..
To simplify (yay!) we have a term that combines all 3:
Molar mass – the mass (in grams) of one mole of a substance
Because this term is broad, we need to be specific in what we are talking about:
Ex. What is the molar mass of oxygen?
Are we talking about molecular oxygen ( O2 )? or atomic Oxygen (O)?
1 mole Oxygen atoms = g O
1 mole O2 molecules = 2 (16.00g) = 32.00g O
We will use (gam) (gmm) or (gfm) instead of molar mass only if we have a situation like this

7. Mass – Mole Relationship
Mass is an easy way to measure quantity of matter, but in chemical reactions, it is often important to consider the number of atoms of each element present in a sample.

8. Demo Problem How many grams are in 9.45 mol of dinitrogen trioxide?
Is this compound ionic, molecular, or an acid?
Molecular (you can tell by the prefixes)
What is the formula?
N2 O3
List the Knowns & Unknowns in your problem
Known: 9.45 moles N2 O3
Molar mass of N2 O3 = ?
1 mol N2O3 = 2(14.01 g N) + 3 (16.00 g O) = 76.02g N2 O3
Solve for the unknown (use dimensional analysis)
9.45 mol N2 O3 (76.02g N2 O3 /1.00 mol N2 O3) = g N2O3
718 g N2 O3

9. Practice Problem How many moles are in 92.2 g of Iron (III) Oxide?
Is this a molecular compound, ionic compound, or acid?
Ionic compound with a transition metal cation
What is the formula?
Fe2 O3
List the knowns and unknowns in your problem
Given mass Fe2 O3 = 92.2 g
1.00 mole Fe2 O3 = 2(55.85g Fe) + 3(16.00gO) = g Fe2 O3
Solve for the Unknown
92.2 g Fe2 O3 (1.00 mol Fe2 O3 / g Fe2 O3 )
= mol Fe2 O3 = mol Fe2 O3

10. Volume – Mole Relationship
The volumes of one mole of different solids and liquids are not the same
1 mole glucose molecules = g glucose
1 mole water molecules = g water
1 mole paradichlorobenzene molecules = g paradichlorobenzene
The volumes of moles of gas are much more predictable if they are under the same conditions

11. Standard temperature and pressure (STP)
The volume of a gas changes with temperature and pressure – so we need a standard reference
Standard temperature and pressure (STP)
Temperature = 0o C
Standard Pressure = kPa = 1 atmosphere(atm)
At STP: 1 mole of any gas occupies a volume of 22.4 L
This is known as the molar volume of a gas and is measured at STP

12. 1 mol of any substance contains 6.02 x 1023 representative particles
Recall..
1 mol of any substance contains 6.02 x representative particles
So…
22.4 L of any gas contains 6.02 x representative particles of that gas.
Does this mean 22.4 L of all gases at STP should have the same mass?
NO. Mass is still measured using molar mass, and 1 mole of each substance has a different mass.

13. Demo Problem
What is the volume (in Liters) of 0.60 mol SO2 gas at STP?
List the knowns and unknowns
0.60 mol SO2
1 mol SO2 = 22.4 L SO2
volume = ? L
Solve for the unknown
0.60 mol SO2 (22.4 L SO2 )/1 mol SO2
13.44 L SO2 = 13 L SO2

14. Density of gas
The density of gas is usually measured in grams per Liter (g/L)
If you are given the density of a gas at STP, you can calculate the molar mass of that gas using the conversion factor
1 mol = 22.4 L

15. Demo Problem
The density of a gaseous compound containing Carbon and Oxygen is g/L at STP. Determine the molar mass of the compound.
Density = g/L
1 mol (gas at STP) = 22.4 L
Convert g/L to g/mol
1.964 g/1.00L (22.4 L/1.00 mol)
= g/mol = 44.0 g/mol

16. The mole road map
We can use the mole to convert between particles, mass, and volume of gas at STP. The mole is the mediator between any of these. So what is the mole road map?

17. Mole Road Map

18. Using the Mole Map.. Find the following.. The mass, in grams of
3.32 mol K
2.50 mol iron (II) hydroxide
The number of moles in
3.70 x g TiO2
75.0 g Nitrogen gas
What is the volume at STP of these gases?
3.20 x mol CO2

19. Practice Problem
What is the density of krypton gas at STP? (hint: assume you have one mole of the gas!)