1.Recall that the coeffcients in a balanced

equation can represent:

1. The number of atoms/molecules

2.The number of moles of atoms/molecules

OHCOOCH 2224 22

1 mol of CH4 molecules

2 mols of O2 molecules

1 mol of CO2 molecules

2 moles of H20 molecules

2. For our purpose,

the mole is a more

practical quantity to

use.

3. From a balanced

equation, such as,

4. it is possible to obtain

mole ratios relating:

1. Reactants to

Reactants

2. Reactants to

Products

3. Products to Products

OHOOH 2222 22

E.g. Hydrazine (N2H4) and hydrogen peroxide

(H2O2) are used for rocket fuel and combine

to produce N2 and H2O gas plus a large

amount of energy according to:

OHNOHHN 222242 42 If it produces a large amount of energy what type

of reaction is this???

The standard method of solving this is using

unitary rates or factors:

OmolesH212OmolesH

HmolesN

2

42

4

1

423 HmolesN

*Think this through in terms of the equation we just

saw... Does this make sense???

OHNOHHN 222242 42

X3 = 12X3 = 3

4.76 moles of H2O2 produces how many moles of water?

2276.4 OmolesH22

2

2

2

OmolesH

OmolesH OmolesH276.4

OHOOH 2222 22

1.The mole ratio used must come from the

balanced chemical equation.

2. In the mole ratio, the quantity that you want to

find goes in the numerator (e.g. 1 mole N2H4).

Building on the mole ratio we looked at...

1. Balancing the equation

2. Mass to Mole Conversions

3. Mole to Mass Conversions

4. Mole Ratios from a balanced equation

1. Mole Mass

2. Mass Mole

3. Mass Mass

E.g. How many grams of water will be produced

when 5.00 moles of hydrogen react with

sufficient oxygen?

Note: If the other reactants are not

mentioned then it’s assumed that there is

enough for the reaction to go to completion.

1) Write the balanced chemical equation.

2) Write in the given information.

OHOH 222 22

OHOH 222 22 5.00 mol

??? g

Moles

underground

Mass

Above

3) Set up a flow diagram for the steps

needed.

4) Perform the appropriate operations.

OHOH 222 22 5.00 mol

??? g

??? mol

Note: Each arrow is a calculation--- doing unit analysis the unit you are

going “from” goes on the bottom, and the unit you are going “to” goes

on the top!

200.5 molH2

2

2

2

molH

OmolH

OmolH

g

21

02.18 OgH21.90

1 mole of any gas at at STP (Standard

Temperature and Pressure)… has a

volume of 22.4 L.

Eg. What is the volume occupied by 0.350mol

of SO2 at STP?

#L = 0.350mol x 22.4L = 7.84L1 mol

C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l)

??? L 10 L

mol CO2mol O2

𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑂2 =

10.0𝐿 𝐶𝑂2 ×1 𝑚𝑜𝑙 𝐶𝑂2

22.4𝐿𝐶𝑂2×

5𝑚𝑜𝑙𝑂2

3𝑚𝑜𝑙𝐶𝑂2×22.4𝐿𝑂2

1𝑚𝑜𝑙𝑂2

= 16.7𝐿𝑂2

50.0𝐿𝐶𝑂2 ×1𝑚𝑜𝑙𝐶𝑂

2

22.4𝐿𝐶𝑂2

×4𝑚𝑜𝑙 𝐻

2𝑂

3𝑚𝑜𝑙𝐶𝑂2

×18.02𝑔 𝐻

2𝑂

1𝑚𝑜𝑙𝐻2𝑂

= 53.6g H2O

C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l)

??? g50 L

mol CO2mol H2O

Consider this reaction…

𝟒𝑵𝑯𝟑 𝒈 + 𝟓𝑶𝟐 𝒈 𝟔𝑯𝟐O(g) +𝟒𝑵𝑶 𝒈

a) What mass of NO is produced when 2.00

mol NH3 are reacted?

b) What mass of H2O is produced when

4.00mol O2 are reacted?

c) What volume of NH3(g) at STP is required to

produce 0.750mol H2O(g) ?

a. 60.02gNO

b. 86.5g H2O

c. 11.2 L NH3(g)

1) Write the balanced chemical equation.

2) Write in the given information.

OHOH 222 22

OHOH 222 22 ??? mol

100.0g

Moles

Here

Masses

Here

3) Set up a flow diagram for the steps

needed.

4) Perform the appropriate operations.

OHOH 222 22

??? mol

100.0 g

??? mol

Note: Each arrow is a calculation---

20.100 gO2

2

00.32

1

gO

molO

2

2

1

2

molO

OmolH OmolH2250.6

1) Write the balanced chemical equation.

2) Write in the given information.

OHOH 222 22

OHOH 222 22

??? g 400.0g

Moles

Here

Masses

Here

3) Set up a flow diagram for the steps

needed.

4) Perform the appropriate operations.

OHOH 222 22 ??? mol

400.0 g

??? mol

OgH20.400OgH

OmolH

2

2

02.18

1 OmolH220.22

??? g

2

2

1

02.2

molH

gH

284.44 gH

OmolH

molH

2

2

2

2 220.22 molH

You can think of the mole as

being a “bridge” between any

unit for a single reactant/

product or between

reactant/product...

Moles and mass› Molecular/ Molar Mass

From the periodic table

Mass of ONE MOLE!!!

Moles and Molecules› Avagadro’s number

Items in ONE MOLE!!!

Moles and Volume (more on these soon)› Concentration of solutions

› Molar volume of gases The moles in ONE LITER!!!

Moles and Moles› Mole Ratio

From the BALANCED CHEMICAL EQUATION!!!

mol

g

molatomsmolecules

1/1002.6 23

Lmol1

molBmolA

A student wants to put 50.0L of Hydrogen gas at STP into a plastic bag by reacting excess aluminum metal with 3.00 Molar (mol/L) Sodium Hydroxide…

2Al(s) + 2NaOH(aq) + 2H2O(l) 2NaAlO2 + 3H2(g)

What volume of NaOH solution is required?

Answer: 0.496L NaOH

Do Review and Practise Questions Sheet

(the Real stuff!)

For Extra Practice at home…

Hebden Pg 127 # 7-12

Hebden Pg 131 # 18-24