Unit 8

Moles & Percent CompositionChapter 10

Words representing Numbers Dozen 12 Baker’s Dozen 13 Gross 144 Ream 500 Mole 6.02 x 1023

Avogadro’s Number 6.02 x 1023

Number of representative particles in a mole

1 mol He = 6.02 x 1023 atoms 1 mol H2 = 6.02 x 1023 molecules

Practice 2 mol H2 = 12.04 x 1023 molecules

2 mol H2 = 24.08 x 1023 atoms

2 mol H2O = 36.12 x 1023 atoms

2 mol C6H12O6 = 72.24 x 1023 O atoms

Mole-Mass relationship 1 mole of any element equals the

atomic mass in grams

1 mol Carbon = 12.01g Carbon

1 mol Iron = 55.8g Iron

Gram Formula Mass Mass of the formula in g/mol Simply add the atomic masses of

each element in the formula together

H2O = 1 + 1 + 16 = 18 g/mol Also known as gram atomic mass,

gram molecular mass, molar mass

Rounding Round most masses to the nearest

whole gram

Except: Copper, Cu 63.5 Chlorine, Cl 35.5

Practice KNO3 = 39 + 14 + 16(3) = 101

g/mol

C6H14 = 12(6) + 1(14) = 86 g/mol

CuSO4 = 63.5 + 32 + 16(4) = 159.5 g/mol

Mole - Mass Conversion

Example: 96 g of Oxygen gas = ? mol

molmolggmol 3/3296#

Practice How many moles are there in 506g

of ethanol, C2H6O?

What is the mass of 8 moles of CCl4?

molggx/46

506

molgxmol/154

8 1232g CCl4

11 mol C2H6O

Mole Road Map

Review How many moles are in 584g of

SF6?

How many grams are in 6 mol of HCl?

X = 584g146 g/mol

= 4 mol

6 mol =X

36.5 g/mol= 219 g

Percent Composition

%100*WholePart

Example H2O

H

100*182

11.1% H

O

100*1816

88.9% O

Another Example NH3

N

100*1714

82.4% N

H

100*173

17.6% H

Percent Composition What is the percent composition of

oxygen in H2SO3?

58.5% 100*8248

Percent Composition What is the percent composition of

aluminum in Al2(SO4)3?

15.8% 100*34254

Percent Composition What is the percent composition of

nitrogen in NH4NO3?

35% 100*8028