Unit 7 : Chp. 7.1-7.5 – Chemical Quantities
7.1
7.2
7.3
The Mole
 Avogadro’s Number
 Relating Formula Units and Avogadro’s
Number
 Calculating Number of Molecules in a Mole
 Calculating Moles of Particles in a Formula Unit
Molar Mass
 Calculating the Molar Mass of a Compound
Calculations Using Molar Mass
 Converting moles of an element or compound
to grams (mass)
7.4
7.5
 Converting grams (mass) of an element or
compound to moles
 Converting grams (mass) or moles to particles
 Converting particles to grams (mass) or moles
% Composition and Empirical Formulas
 Calculating % Composition
 Calculating Empirical Formulas
Molecular Formulas
 Relating empirical and molecular formulas
 Calculating molecular formulas
I Can Statements:
(7.1) THE MOLE
1. I can use Avogadro’s number to determine the number of particles in a given number of moles.
2. I can recognize that 1 mole of a substance is equivalent to 6.02 x 1023 units of that substance.
3. I can understand the mole as a manageable quantity that is used to count a large number of very
small particles.
(7.2, 7.3) MOLAR MASS and CALCULATIONS USING MOLAR MASS
1. I can relate the unit of previously studied molecular mass in atomic mass units (a.m.u.) to molar mass
in grams per mole (g/mol).
2. I can use molar mass to make calculations and conversions involving elements and compounds
3. I can use the periodic table to calculate molar mass for compounds given their formulas.
4. I can use molar mass as a conversion factor to convert between mass in grams to amount in moles.
5. I can recognize the ratio of moles of the elements that make up a compound given the formula.
6. I can calculate the moles of a particular element in a compound when given the total number of moles
of the substance.
7. I can use molar mass and Avogadro’s number to convert between mass, moles, and number of
particles.
(7.4, 7.5) PERCENT COMPOSITION, EMPIRICAL FORMULAS and MOLECULAR FORMULAS
1. I can use molar mass to calculate the percent composition of a compound by mass.
2. I can define and contrast empirical formulas and molecular formulas of a compound.
3. Given the relative masses of elements in a compound, I can determine the empirical formula.
4. Given the empirical formula and the molar mass of a compound, I can determine the molecular
formula.
Vocabulary
6.022 x 1023
Avogadro’s number
element ratio
empirical formula
formula unit
molecular formula
molar mass
mole
mole ratio
percent composition
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Achievement Scale
Goal
7.1
The Mole
7.2
Molar Mass
7.3
Calculations Using Molar Mass
C Level
Given the molar mass and a
flow chart of conversions, I
can calculate the molar mass
when given a chemical
formula and perform one step
conversions using the molar
mass or Avogadro’s number
as conversion factors.
B Level
I can calculate
the molar
mass when
given a
chemical
formula and
perform
multistep
conversions
using the
molar mass or
Avogadro’s
number as
conversion
factors.
Given the molar mass and
number of atoms of each
element, I can calculate
percent composition for a
compound.
Given the molecular formula, I
can determine the empirical
formula of a substance.
Given the
molar mass
and chemical
formula, I can
calculate
percent
composition
for a
compound.
Given the
percent
composition, I
can determine
the empirical
formula of a
substance.
I can use Avogadro's Number
and Mole Mass to determine
Chemical Quantities.
7.4
% Composition and Empirical Formulas
7.5
Molecular Formulas
I can calculate Percent
composition of a compound.
I can calculate empirical and
molecular formulas for a
substance.
A Level
I can perform
multistep
conversions using
the molar mass or
Avogadro’s number
as conversion
factors, including
conversions from
molecules to
individual elements
within the
molecule.
Given the chemical
formula, I can
calculate percent
composition for a
compound.
Given the percent
composition and
the molar mass, I
can determine the
empirical and
molecular formulas
of a substance,
including formulas
with multipliers.
2
Sample Questions and Test Grade Recovery for 7.1 – 7.5
C Level:
1. What are formula units and moles and how are they different from one another?
2.
3.
What are the element ratio and mole ratio in (NH4)3PO4?
(a) Calculate the number of iron atoms in 2.50 moles of iron. Follow ALL math work rules!
(b) Calculate moles of water molecules represented by 3.55 x 1025 water molecules. Follow ALL
math work rules!
5.
𝑔
(a) Convert 4.55 moles of MgCO3 to grams. The Molar mass of MgCO3 is 84.32 𝑚𝑜𝑙
(b) Convert 75.0 g of MgCO3 to mass in grams.
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(c) Calculate the % composition of MgCO3
7. What is the empirical formula of each of the following?
a) C6H12O6, glucose
b) N2H4, hydrazine
c) C6H6, benzene
d) NH3, ammonia
8. Phosphine is a highly toxic compound used for pest and rodent control. If a sample of phosphine contains
0.0147 mol of P and 0.0436 mol of H, what is the empirical formula? Follow ALL math work rules!
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1. Glyoxyl, used in textiles has the empirical formula, CHO. What is the molecular formula if glyoxyl’s
molecular molar mass is ≈ 58 g/ mol? Follow ALL math work rules!
B Level:
1.
(a) What is the molar mass of allyl sulfide, (C3H5)2S
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(b) How many grams of allyl sulfide, are in 4.20 x 1023 molecules of allyl sulfide? Follow
ALL math work rules!
(c) How many particles of allyl sulfide are there in 15.0 g of allyl sulfide? Follow ALL math work
rules!
2 Sulfate of potash is the common name of a compound used in fertilizers to supply potassium and sulfur.
What is the empirical formula of this compound if it has a percent composition of 44.9% K, 18.4 % S, and
36.7 % O? Follow ALL math work rules.
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3. The insecticide lindane has a percent composition of 24.78 % C, 2.08 % H, and 73.14 % Cl. If its molar
mass is about 291 g/ mol, what is the molecular formula? Follow ALL math work rules!
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A Level:
1. Calculate the empirical formula for the following substance. Follow ALL math work rules!
19.8 % C, 2.20 % H, and 78.0 % Cl
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2. Chloral hydrate, a sedative, contains 14.523 % C, 1.828 % H, 64.303 % Cl, and 19.346 % O. If it has a
molecular molar mass of about 165 g, what is the molecular formula of chloral hydrate? Follow ALL math
work rules!
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