Chapter 10 Chemical Quantities Yes, you will need a calculator
for this chapter!
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Section 10.1 Da Mole: A Measurement of Matter
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How do we measure items? Measure mass in. Measure volume in.
Measure amount in.
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What is the mole? Were not talking about this kind of
mole!
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Moles (mol) It is. Defined as the number of carbon atoms in
exactly 12 grams of carbon-12. of representative particles. 6.02 x
10 23 is called: number. 1 mole = 6.02 x 10 23 = Avogadros
number
What are Representative Particles? The smallest pieces of a
substance: based on what were looking at 1)For a molecular
compound: it is the. 2)For an ionic compound: it is the formula
unit (ex: NaCl, MgS). 3)For an element: it is the. 1 mol of CO 2, 1
mol of NaCl, and 1 mol of H equal 6.02 x 10 23 of that thing.
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Measuring Moles The mass on the PT is also the mass (g/mol)
mass (in grams) of 1 mole of that atom =
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Nitrogen Aluminum Zinc Find the Molar Mass (g/mol) of the
following:
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What about compound mass? In 1 mole of H 2 O, there are moles
of H atoms and mole of O atoms To find the mass of a compound:
Determine of each element present the number times their mass (from
the periodic table) them up for the
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Calculating Compound Mass Calculate the mass of magnesium
carbonate, MgCO 3.
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Practice Problem: What is the mass of one mole of CH 4 ? 1 mole
of C = 12.01 g/mol 4 mole of H x 1.01 g = 4.04g/mol 1 mole CH 4
=
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10.1 Review 1.1 mol = particles 2.2.5 mol MgCl 2 = ? particles
MgCl 2 = 3.7.2 x 10 24 Fe particles = ? mol Fe =
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4. Molar mass of BeF 2 = 5. Molar mass of C 6 H 12 O 6 = Be =
9.0 g/mol F = 19.0 g/mol C = 12.0 g/mol H = 1.0 g/mol O= 16.0
g/mol
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Section 10.2 Mole-Mass and Mole-Volume Relationships
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Since Molar Mass is Number of in 1 mole. grams per mole (g/mol)
Use to make _ factors from these. - Use molar mass to convert to or
of a substance.
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For example How many moles is 5.69 g of NaOH? = How many grams
in.53 mol of NaOH? =
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Practice Problems: How much would 2.34 moles of carbon weigh?
How many moles of magnesium is 24.31 g of Mg?
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The Mole-Volume Relationship Under different circumstances,
can. Two things effect the volume of a gas: a) Temperature and b)
**We need to compare all gases at the same temperature and
pressure.
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Standard Temperature and Pressure abbreviated (273K) and
pressure At STP 1 mole of gas occupies 22.4 L= molar volume of any
gas at STP
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Practice Problems: What is the volume of 4.59 mole of CO 2 gas
at STP? How many moles is 5.67 L of O 2 at STP?
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What is the volume of 8.8 g of CH 4 gas at STP? =
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Summary: These four items are all : a) 1 mole b) molar mass (in
grams/mol) c) particles (atoms, molecules, or formula units) d) of
a gas at **Thus, we can make factors from them.
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Avog. # Practice problems: How many molecules of CO 2 are in
4.6 moles of CO 2 ? How many moles of water is in 5.87 x 10 22
molecules? How many atoms of carbon are in 1.230 moles of Carbon?
How many moles is 7.78 x 10 24 formula units of MgCl 2 ?
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Mixed Practice Problems: How many atoms of lithium is 1.0 g of
Li? How much would 3.45 x 10 22 atoms of U weigh? What is the
volume of 10.0 g of CH 4 gas at STP?
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Section 10.3 Percent Composition and Chemical Formulas
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Percentage Composition Percentage by of element in a
compound
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Calculating Percent Composition of a Compound Like all percent
problems: part whole 1)Find mass of (from the periodic table)
2)Next, divide by total mass of ; then _ x 100 % = _
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Percentage Composition Find the % composition of Cu 2 S. %Cu =
%S =
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%H 2 O = Find the mass percentage of water in calcium chloride
dihydrate, CaCl 2 2H 2 O? Percentage Composition
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Empirical Formula (EF) whole number of atoms in a compound
C2H6C2H6C2H6C2H6 simplify subscripts
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Empirical Formula (EF) Just find whole number ratio C 6 H 12 O
6 CH 4 N Formula is not just ratio of atoms, it is also ratio of.
In 1 mole of CO 2 there is mole of carbon and moles of oxygen. In
one molecule of CO 2 there is 1 atom of C and 2 atoms of O. =
already lowest ratio.
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Formulas (continued) Formulas for compounds are ALWAYS
empirical (the lowest whole number ratio = be reduced). *Remember,
we simplify beforehand Examples: NaClMgCl 2 Al 2 (SO 4 ) 3 K 2 CO
3
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Formulas (continued) Formulas for molecular compounds be
empirical (lowest whole number ratio). Molecular: C 6 H 12 O 6 C 12
H 22 O 11 Empirical: H2OH2O (Correct formula) (Lowest whole number
ratio)
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Formulas Empirical Formula (EF) = lowest whole number ratio of
elements in a compound. Molecular Formula (MF) = the actual ratio
of elements in a compound. The two can be the same. CH 2 = C 2 H 4
= C 3 H 6 =H 2 O =
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Calculating EF We can get a ratio from the percent composition.
1.) Assume you have 100 g. -the percentage becomes grams (75.1% =
75.1 grams) 2.) Convert grams to moles. 3.) Find lowest whole
number ratio by dividing by the smallest # of moles. **4.) If not a
whole #, use a multiplier.
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Example Calculate the empirical formula of a compound composed
of 38.67 % C, 16.22 % H, and 45.11 %N. Assume 100 g so: 38.67 g C x
1mol C = 3.220 mole C 12.01 gC 16.22 g H x 1mol H = 16.06 mole H
1.01 gH 45.11 g N x 1mol N = 3.220 mole N 14.01 gN Now divide each
value by the smallest value
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Example 3.220 mol C = 1 mol C 3.220 16.06 mol H = 5 mol H 3.220
3.220 mol N = 1 mol N 3.220 EF = C 1 H 5 N 1 = CH 5 N
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Empirical Formula (EF) Find the empirical formula for a sample
of 25.9% N and 74.1% O. 25.9 g 1 mol 14.01 g = 1.85 mol N 74.1 g 1
mol 16.00 g = 4.63 mol O 1.85 mol = 1 N = 2.5 O
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Empirical Formula N 1 O 2.5 Need to make the subscripts whole
numbers multiply by 2 N2O5N2O5N2O5N2O5
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EF Practice Find the empirical formula for a sample of 43.64% P
and 56.36% O.
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Molecular Formula (MF) True Formula - the actual number of
atoms in a compound CH 3 C2H6C2H6C2H6C2H6 empiricalformula
molecularformula ?
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Empirical to Molecular Since the empirical formula is the
lowest ratio, the actual molecule would weigh more. By a whole
number multiple. **Divide the actual molar mass by the empirical
formula mass.
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Molecular Formula The empirical formula for ethylene is CH 2.
Find the molecular formula if the molecular mass is 28.1 g/mol?
28.1 g/mol 14.03 g/mol = 2 empirical mass = 14.03 g/mol (CH 2 ) 2 C
2 H 4
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Practice Problem: Caffeine (EF= C 4 H 5 N 2 O) has a molecular
mass of 194 g. What is its molecular formula?
