UNIT 2
TOPIC 1: QUANTITATIVE CHEMISTRY
Assessment Statements
Objective
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
1.1 The mole concept and Avogadro’s constant
 Apply the mole concept to substances.
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 Determine the number of particles and the amount of substance (in moles).
3
1.2 Formulas
 Define the terms relative atomic mass (Ar) and relative molecular mass (Mr).
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 Calculate the mass of one mole of a species from its formula.
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 Solve problems involving the relationship between the amount of substance in
3
moles, mass and molar mass.
 Distinguish between the terms empirical formula and molecular formula.
2
 Determine the empirical formula from the percentage composition or from other 3
experimental data.
 Determine the molecular formula when given both the empirical formula and
3
experimental data.
1
1.3 Chemical equations
 Deduce chemical equations when all reactants and products are given.
 Identify the mole ratio of any two species in a chemical equation.
 Apply the state symbols (s), (l), (g) and (aq).
1.4 Mass and gaseous volume relationships in chemical reactions
 Calculate theoretical yields from chemical equations.
 Determine the limiting reactant and the reactant in excess when quantities of
reacting substances are given.
 Solve problems involving theoretical, experimental and percentage yield.
 Apply Avogadro’s law to calculate reacting volumes of gases.
 Apply the concept of molar volume at standard temperature and pressure in
calculations.
 Solve problems involving the relationship between temperature, pressure and
volume for a fixed mass of an ideal gas.
 Solve problems using the ideal gas equation, PV = nRT
 Analyse graphs relating to the ideal gas equation.
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3
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3
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1.5 Solutions


Distinguish between the terms solute, solvent, solution and concentration
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(g dm–3 and mol dm–3).
Solve problems involving concentration, amount of solute and volume of solution.
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Measurement and Units
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Standardized system of measurement – Systeme International
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SI Units
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Typical units used in the lab
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SI Prefixes – converts a base unit to a unit that is appropriate for the
measurement
Temperature

By definition temperature is a measure of the
•
In scientific measurements,
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The Celsius scale is based on the
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0C is the
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100C is the
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Kelvin is the SI
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It is based on the
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There are no negative
K=
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Dimensional Analysis
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We use dimensional analysis to
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Most commonly dimensional analysis utilizes
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Use the form of the conversion factor that puts the
Problem Solving In Chemistry
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Answers will always include
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Correct
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Correct
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Estimated
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Correct
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Examples: Dimensional Analysis
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Convert 8.00 m to inches.
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An aspirin tablet contains 325 mg acetaminophen. How many grams is this
equivalent to?
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Example: Units to a Power How many m3 is 1500 cm3?
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Example: Converting Multiple Units:The density of aluminum is 2.70 g/cm3.
Express this value in units of kilograms per cubic meter.
Amounts of a Substance
What is a mole?
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An amount of substance that contains
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Analogy
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A dozen
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A ream
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A mole
Avogadro’s Number
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CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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Example: Determine the number of atoms of C-12 in one mole if the mass of 1
atom of C -12 is 1.99252 x 10 -23 g.
Relative Molecular Mass (Mr)
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By definition, Mr is the mass of
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The relative molecular mass of an element is the
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The Mr of a compound is the sum of each of the
Example: Calculating Molar Mass
Calculate the molar mass for each of the following elements/compound:
1. CO2
2. H2SO4
3. S
4. Ca(C2H3O2)2
Using Moles
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Moles provide a bridge
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If the substance is an element
Converting to determine number of Particles
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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Equation:
Where
n=
N=
L=
Examples: Using Avogadro’s Number
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How many atoms of Au are there in 0.36 moles of Au?
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How many moles are there in 3.46 x 1028 molecules of water?
Converting Between Mass and Moles
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Equation:
Where
n=
m=
Mr =
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Example: Using Moles in Calculations – Molar Mass
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How many moles of tin are there in 250 grams of tin?
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How many moles of SO2 is present in 0.45 grams of sulfur dioxide?
Mole Relationships
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One mole of atoms, ions, or molecules contains
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One mole of molecules or formula units contains
Molecules and Chemical Formulas
Molecules
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Molecules are groups of
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Molecules may be
Molecular Elements and Allotropes
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CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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Some Elements exist as molecules
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Diatomic
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Phosphorus exists
Some elements exist in a variety of forms (Allotropes)
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Carbon:
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Phosphorus -
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Sulfur –
Diatomic Molecules
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These seven elements occur naturally as molecules containing two atoms.
Molecules and Molecular Compounds
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Molecular compounds –
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Covalent bonds –
Formulas
•
A compound is represented by
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Subscripts are used to indicate how
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If there is only one atom of a
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Changing the
•
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consider
Two different compounds can,
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dimethyl ether and ethyl alcohol both
Ions
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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When atoms lose or gain electrons, they become ions.
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Cations are
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Anions are
How charged species arise
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Neutral atoms and molecules
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Cations have more protons
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Anions have more electrons
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Common Monatomic Ions
Main Group Elements
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Group 1, 2 – All Metals –
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Group 3 – Metals (doesn’t include B) –
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Group 5 – Non Metals –
Metal – Bi –
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Group 6, 7 – Non Metals
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Group 0 – Doesn’t Form Ions!!
Common Variable Charge Cations
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Copper –
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Iron –
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Lead –
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Gold –
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Tin –
Ionic Bonds
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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Ionic compounds (such as NaCl) are generally formed between
Writing Formulas
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Because compounds are electrically neutral, one can determine the formula of a
compound this way:
•
The charge on the cation
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The charge on the anion
•
If these subscripts are not in the
Examples: Writing the Formula for Ionic Compounds
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Ca and Cl
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Ba and F
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Na and S
Polyatomic ions
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Cations or anions consisting of
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When more than one appears in a formula unit –
•
example:
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Polyatomic Ions to Memorize
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Ammonium
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Hydrogen Carbonate (Bicarbonate)
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Carbonate
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Nitrate
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Hydroxide
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Sulfate
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Acetate (Ethanoate)
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Phosphate
Types of Ionic Compounds
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Ionic compounds will always consist of one of the following combinations:
•
a
•
a
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a
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two
Properties of Ionic Compounds
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High melting points that
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Most ionic solids
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Most ionic
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Solutions of ionic compounds
•
In ionic substances, each ion has its own characteristics,
Binary Compound Nomenclature
Ionic Nomenclature
•
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Write the name of the cation.
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If the cation is a
•
If the cation can have more than
If the anion is an element, change its ending to
•
If the anion is a polyatomic ion,
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Examples Formula to Name
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NaCl
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MgCl2
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KBr
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CuCl
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CuCl2
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Al(NO3)3
Example Name to Formula
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Sodium sulfate
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Barium chloride
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Ammonium nitrate
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Copper (II) nitride
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Silver oxide
Binary Molecular Nomenclature
Nonmetals + nonmetals
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Name nonmetal further
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Name nonmetal further to the
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Use Greek prefixes to
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Greek prefixes
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Examples
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N2O3
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CO2
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P2O5
Acids
•
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Binary acids –
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name
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then add
•
end with
Examples
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HCl –
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H2S –
Oxyacids
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Take polyatomic suffix and convert
•
change
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change
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Do not use
•
Examples
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H2SO4 –
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H2SO3 -
Hydrates
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Some ionic compounds can have
•
These compounds are termed
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Naming Hydrates
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Hydrates are named by naming the ionic compound and
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Example
CuCl2 5H20
Formula Calculations
Types of Formulas
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Empirical formulas give the
•
Molecular formulas give the
Empirical Formula
•
Simplest whole number
•
All ionic
•
Molecular formulas are either
The composition of compounds
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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Mole composition is the number of
•
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CO2 -
Mass composition is the
•
CO2 -
Percent composition
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Equation
Example
Find the mass % of each element in CH2O (formaldehyde)
Calculating Formulas
Determination of Empirical formula
•
Problem Solving Process:
Example
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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A compound contains 63.6% N and 36.4% O, determine the compounds
empirical formula
Example
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Determine the empirical formula for a compound which is 26.6% K, 35.4% Cr,
38.0% O
Molecular formula
•
The actual number of
•
Consider acetylene and benzene
•
both have the
•
acetylene is
•
benzene is
Molecular Formula from Empirical
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Molecular formula must be
•
Therefore the mass of the
Example
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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A compound has the following composition 20.0% C, 2.2 % H, 77.8 % Cl. The
molar mass of the compound is 545 g/mol. What is the molecular formula of the
compound
States of Matter
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
States of Matter
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The three states of matter are described in terms of molecular motion,
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The state of matter is
Changes of State
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When the temperature increases enough for the particles to have
Chemical Reactions
What is a Chemical Equation?
•
Shows the
4 Al(s) + 3 O2(g)  2 Al2O3(s)
State Symbols
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Solid
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Liquid
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Gas
•
Aqueous (aq) –
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Chemical Equations
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4 Al(s) + 3 O2(g)  2 Al2O3(s)
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This equation means
Chemical Equations
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Because the same atoms are present in a
•
This represents the
•
Chemical reactions are
Tips for Balancing Equations
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You can never change a
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The coefficient applies as a
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Atoms on the same
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Balance
Balancing Equations
___ Al(s) + ___ Br2(l)  ___ AlBr3(s)
Examples: Balancing Equations
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
____C3H8(g) + _____ O2(g)  _____CO2(g) + _____ H2O(g)
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Stoichiometry
STOICHIOMETRY
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the study of the
•
It rests on the
Problem Solving Process
1. Write the balance chemical equation
2. Convert given amounts into moles, if amounts for each reactant is given convert
both amounts into moles to determine the limiting reactant (more on this later)
3. Use the mole – mole relationships from the reaction to convert from the moles
you have to the moles of the other substance you want
4. Convert to the desired quantity requested and be sure your answer has the
correct units and correct significant figures. (this is called a theoretical yield)
Example
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If 454 g of NH4NO3 decomposes, how much H2O is formed? What is the
theoretical yield of the water?
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
NH4NO3  N2O + H2O
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Finding the Theoretical Yield
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% Yield =
Example
•
Ethyne (Acetylene) is used in welding as its combustion gives a lot of heat.
2 C2H2 + 5O2  4CO2 + 3H2O
Calculate the mass of CO2 produced from the complete combustion of 1.00g
of C2H2?
Reactions Involving a LIMITING REACTANT
LIMITING REACTANTS
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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Example: Limiting Reactants : If 5.40 g of Al is mixed with 8.10 g of Cl2. What
mass of AlCl3 can form?
Al(s) + Cl2(g)  AlCl3 (s)
Finding the Amount of Reactant in Excess
•
Cl2 was the limiting reactant.
•
Therefore, Al was present in excess. But how much?
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First find how much Al was required.
•
Then find how much Al is in excess.
Calculating Excess Al
Reacting Gases
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Volumes of Reacting Gases
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Gay – Lussac’s Law – through observation he found that when gases react,
Example – Reacting Gases
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40 cm3 of carbon monoxide reacts with 40 cm3 of oxygen according to the
following reaction. What volume of carbon dioxide is produced? Assume that
the reaction takes place at the same temperature and pressure.
2CO(g) + O2(g)  2CO2(g)
Molar Volume of Gas
Molar Volume
•
Molar Volume –
•
Use – to calculate the
Example – Molar Volume
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Calculate the amount in moles of chlorine gas in 44.8 cm3 of the gas at STP.
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Example: Molar Volume
How many liters of hydrogen can be produced by reacting 4.0 g of aluminum with
excess hydrochloric acid if the hydrogen is collected at STP.
2Al(s) + 6 HCl(aq)  2AlCl3(aq) + 3H2(g)
The Gas Laws
Pressure
•
Pressure – result of collisions
•
SI Unit for Pressure –
•
Helpful conversions
•
N=
•
1.00 atm =
•
1.00 atm =
Boyles Law
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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The volume of a fixed quantity of
Graphical Representation
•
A plot of V versus P results in a curve.
Example: Boyles Law
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The volume of some amount of a gas was 1.00 dm3 when the pressure was 10.0
atm; what would the volume be if the pressure decreased to 1.00 atm?
Charles Law
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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The volume of a fixed amount of gas at constant pressure is directly proportional
to its absolute temperature.
Example: Charles Law
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A gas occupied a volume of 6.54 dm3 at 25°C what would its volume be at 100°C?
Amontons Law
•
The pressure of a gas is directly related to absolute temperature of gas at
constant volume.
•
Relationship
Combined Law
•
This law combines Boyle’s Law, Charles’s Law and Amonton’s Law so that the only
constant variable is the amount (moles) of gas.
Example: Combined Law
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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What happens to the volume of a fixed amount of gas when the pressure and
absolute temperature are both doubled?
Example: Combined Law
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A 1.00 dm3 balloon at 25.0oC has a pressure of 750 mmHg. If the temperature is
increased to 37.0oC and the pressure is decreased to 740 mmHg, what is the new
volume?
Ideal Gas Equation
•
So far we have seen that:
•
Combining these into one relationship:
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Proportionality Constant R
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The constant of proportionality is known.
•
IB Uses
Ideal Gas Equation
•
The relationship:
•
Becomes:
Example – Ideal Gas Law
•
If I have 0.275 moles of gas at a temperature of 275 K and a pressure of 1.75
atmospheres, what is the volume of the gas in dm3?
Example – Ideal Gas Law
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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If I have an unknown quantity of gas held at a temperature of 1195 K in a
container with a volume of 25 dm3 and a pressure of 560 atm, how many moles
of gas do I have?
Calculating the Molar Mass
•
Molar Mass (M)
M=
Calculating the Density
•
Density
Example: Molar Mass
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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A gaseous sample of a compound has a gas density of .977 g/L at
710.0 torr and 100oC. What is the molar mass of this compound?
Example: Finding Density
•
What is the density of acetone, C3H6O, vapor at 730 mmHg
and 127oC?
Solutions
Solutions
•
Solute –
•
Solvent –
•
Solution –
•
Aqueous solutions –
Concentration
•
Concentration –
•
Saturated solution –
•
Common Concentration units –
•
[Concentration] =
Example: Concentration
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
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A solution contains 4.10 g of NaCl in 1.00 dm3. What is the solutions
concentration in g dm-3 and mol dm-3.
Standard Solution
•
Definition –
•
Calculating the amount of solute needed to make a standard solution –
Concentration =
Example: Making a Standard Solution
•
Calculate the mass of NaOH need to make 250 cm3 of a 0.200 mol dm-3 solution.
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
Titrations
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Titrations
•
Laboratory Technique –
Example: Titration
What volume of 0.100 mol dm-3 NaOH is required to titrate 25 mL of 0.300 mole dm-3
solution of HCl to produce a neutral solution?
Calculations involving solutions and Gases
Example
•
CDO IB Chemistry SL/HL Unit 2 2013 Quantitative Chemistry Topic 1
‘
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Calculate the volume of carbon dioxide produced when 1.00 g of calcium
carbonate reacts with 20.0 cm3 of hydorchloric acid. Assume the volume of the
gas is measured at STP