Download - Mole – chemical unit of amount
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