Brad Ashburn, PhD Biochemistry 141

Module 9

The Mole

2

A mole is a quantity that contains 6.02 x 1023 items

Avogadro’s Number

Examples

3

How many molecules are in 3.00 moles of CO2?

How many moles are 8.7 x 1024 molecules of CO2?

Molar Mass

4

The molar mass is the mass (in grams) of one mole of any substance

Molar mass comes from the Periodic Table

5

Calculate the number of moles present in 152.6 g of the anti-depressant Li2CO3.

Grams to Moles Conversion

Moles to Moles Conversion

6

2C2H6 + 5O2 4CO + 6H2O

What are the coefficients telling us?

7

N2 + 2O2 2NO2

How many moles of NO2 are formed from 3.3 moles of N2?

Grams to Grams Conversion

8

Grams to Grams Conversion

9

mole–mole conversion

factor

molar mass conversion

factorGrams of reactant

molar mass conversion

factor

Moles of reactant

[1]

Moles of product

[2]

Grams of product

[3]

Example

10

Ethanol is made by reacting ethylene gas with water. How many grams of ethanol are formed from

14 grams of ethylene?

C2H4 + H2O C2H6O

Concept Check 1

11

The principle component of natural gas is methane, CH4, which undergoes a general combustion reaction below:

CH4 + O2 -----> CO2 + H2O

Write out the balanced chemical reaction.

How many grams of CO2 are produced from 5.50 grams of O2? Show your work.

Concept Check 2

12

The active ingredient in many commercial antacids is calcium hydroxide, Ca(OH)2, which reacts with stomach acid (HCl) to produce calcium chloride (CaCl2) and water:

Ca(OH)2 + HCl ----> CaCl2 + H2O

Write out the balanced reaction.

Classify the reaction.

How many grams of stomach acid (HCl) are needed to produce 12.8 g of CaCl2?

Energy Change in Chemical Reactions

13

ΔHWhen energy is absorbed, the reaction is

endothermic and ΔH is positive.

When energy is released, the reaction is exothermic and ΔH is negative.

Energy Change in Chemical Reactions

6CO2(g) + 6H2O(l) C6H12O6(aq) + 6O2(g)

ΔH = +678 kcal

CH4(g) + 2O2(g) CO2(g) + 2H2O(l)

ΔH = -213 kcal14

When ΔH is positive:

When ΔH is negative:

Reaction Rate

15

Three Factors determine the rate of a chemical reaction.

ConcentrationTemperature

Catalyst