MOLE – Chemical unit of amount

• Refers to the amount of a substance which contains the same number of pieces as there are the number of atoms of Carbon in 12 grams of C12

• 12 grams C12 = 6.02 x 1023 atoms of Carbon = 1 mole

• 1 mole any substance = 6.02 x 10 23 pieces• • 1 mole of O atoms = 6.02 x 10 23 O atoms• 1 mole Na atoms = 6.02 x 10 23 Na atoms• 1 mole of H2O = 6.02 x 10 23 H2O molecules• 1 mole of apples = 6.02x 1023 apples

Molar Mass – mass in grams of 1 mole of a substance

• G atomic mass- mass in grams of 1 mole of atoms that is numerically equal to its atomic mass

• 22.9Na11

• g-molecular mass – mass in grams of 1 mole of molecules that is numerically equal to its molecular mass (sum of all atomic masses of atoms comprising the molecule if the formula of the molecule is known)

H2O

1 mole x 15.9 = 15.92 moles x 1 = 2

17.9 g

H2O

1mole x 16 = 162 moles x 1 = 2

18 g

or

NaCl

1 x35.45 = 35.451 x 23 = 23

58.45 g G formula mass

G molecular mass

Molar Mass – mass in grams of 1 mole of a substance

• g – formula mass – mass in grams of 1 mole of formula units that is numerically equal to its formula mass ( sum of all atomic masses of atoms comprising the formula unit if formula of the compound is known)

H2O

1 mole x 15.9 = 15.92 moles x 1 = 2

17.9 g

H2O

1mole x 16 = 162 moles x 1 = 2

18 g

or

NaCl

1 x35.45 = 35.451 x 23 = 23

58.45 g G formula mass

Molar Mass

G atomic mass

Gram molecular mass

Gram formula mass

Can be said to be

substance

Element

molecule

Formula unit

when

Is a MOLE a number or a mass ?

• It is both.

• MOLE = 6.02 X 10 23 = Molar mass

Exercise VII: Chemical Quantities

Exercise Vii

Problem Categories Of the Mole

Concept

I. Conversion between G,moles,

pieces

II. Calculation Involving

Composition

III. Stoichiometry in a balanced chemical

equation

Category I : Conversions between mole , grams, atoms, moleculesCalculation where information about the quantity of the substance is sought from a

given quantity of the same substance

mole

pieces

Gram

1 mole = molar mass

1 mole = Avogadro’s Number

Equivalent factor

Calculation where information about the quantity of the substance is sought from a given quantity of the same substance

Category I : Conversions between mole , grams, atoms, molecules of a given substance

• How many moles of sulfur atoms are there in 8.23 grams of sulfur, S ?

mole

Gram

1 mole = molar mass Equivalent factor

? S

8.23 g S

1 mole S = 32 g S

mole S = 8.23 g S

1 mole S_ _ _ _ _ _ 32 g S

X

Calculation about Composition

• Calculations where informations about the quantities of a substance are sought from the given amounts of the compound containing the substance.

• conversion factors

• ?gram pieces

mole

mole

gram pieces

compound

Element /component

Formulasubscripts

?

??

• E.g. How many grams of Cl are contained in 20 grams of CCl4 ?

7.76 g C8H10N4O2 ( caffeine) X

1 mole caffeine_ _ _ _ _ _ _ 194 g caffeine

X8 moles C_ _ _ _ _1 mole caffeine

X

12 g C_ _ _ _1 mole C

= 3.84 g C

How many grams of C are present in 7.76 g caffeine ?

Other calculations

• Percent Composition• Emperical Formula Determination• Molecular Formula Determination

• Emperical Formula = formula which shows the smallest whole number ratio of atoms of the elements comprising the compound.

• Molecular Formula = formula which shows the actual number of atoms of the elements comprising the compound.

Stoichiometry- Quantitative Calculations of substances in a balanced chemical equation

1. Mole- molecalculation2. Mole-mass calculation3. Mass-mass

calculation4. Limiting

Reactant Calculation

Stoichiometry- Quantitative Calculations of substances in a balanced chemical equation

• Determination of theQuantity of a substanceFrom a known quantityOf another substance In a balanced chemical• equation

reactant reactant product

reactant product product

Can be

Can be

Individual amountsOf reactants neededTo react

Individual amounts of products produced

tells

• 1 mole CH4= 2 moles O2

• Individual moles of reactants needed to react

• 1 mole CO 2 = 2 moles H2O

• Individual moles of products produced

CH4 2 O2 + CO2 2 H2O+

To be used as conversion factors

Conversion Map : category III

gram

pieces

mole

gram

mole

pieces

Balanced equation

Reactant versus reactantReactant versus productProduct versus product

?

C2H5OH O2 CO2 H2O+ +3 2 3

Mole O2 = 10. O mole C2H 5 O H X

3 moles O2_ _ _ _ _

1 mole C2H5OH

CO2mole = C2H5OH50.0 g XC2H5OH1 mole

C2H5OH46 g

CO22 moles

C2H5OH1 moleX

= 30 moles

= 2.17 moles CO 2

Mole ?50.0 g

C2H5OH O2 CO2 H2O+ +3 2 3

G ?10 g

G O2 = 10 g C2H5OHC2H5OH

X1 mole

46 g C2H5OH

3 moleO2

1 mole C2H5OHx

32 g O2

1 mole O2

X

20.86 grams of O2