🧷
Chapter 1 Stoichiometric
Relationships
Chapter.Section
1
Created
June 25, 2021 1042 AM
Tags
Chemistry HL
Exercises Column
Summary Column
1.1
1.2
1.3
Notes Column
1.1 Introduction to the particulate nature of matter and chemical change
Chemical Equations Summarize Chemical Change
Mixtures form when substances combine without chemical reaction
Matter exists in different states determined by the temperature and the pressure
Matter Changes State Reversibly
Quick Summary
1.2 The Mole Concept
The Avogadro constant defines the mole as the unit of amount in chemistry
Relative Atomic Mass is Used to Compare the Masses of Atoms
Molar Mass is the Mass of one mole of a substance
The Empirical Formula of a Compound Gives the Simplest Ratio of its Atoms
Percentage Composition by Mass can be calculated from the empirical formula
The Molecular Formula of a Compound Gives the Actual Number of Moles in a
Molecule
Combustion Analysis Usually Gives Data on The Mass of Compounds Formed
Quick Summary
1.3 Reacting Masses and Volumes
Chemical Equations Show Reactants Combining in a Fixed Molar Ratio
The Theoretical Yield is Determined by the Limiting Reactant
The Percentage Yield Can Be Calculated From the Experimental and Theoretical
Yields
Avogadro's Law Directly Relates Gas Volumes to Moles
All Gases Under the Same Conditions Have the Same Molar Volume
Chapter 1 Stoichiometric Relationships
1
A note about the units of volume
The Gas Laws Describe Pressure, Volume, and Temperature Relationships for All
Gases
A Notes About Units of Temperature
A Note About Units of Pressure
1. Relationship Between Volume and Pressure
2. Relationship between Volume and Temperature
3. Relationship Between Pressure and Temperature
The Ideal Gas Equation is Derived from the Combined Gas Equation and Avogadro's
Law
Real gases show deviation from ideal behavior
The concentration of a solution depends on moles of solute and volume of solution
Dilutions of Solutions Reduce the Concentration
The Concentration of a Solution Can be Determined by Volumetric Analysis
Exercises Column
1.
a. CuCO3
→ CuO + Co2
b. 2Mg + O2
→ 2MgO
+ 2NaOH →
Na2 SO4 + 2H2 O
c. H2 SO4
Summary
Column
1.1
Basic Definitions that include:
Chemical Element
d. 3H2
+ N2 → 2NH3
Combustion
e. CH4
+ 2O2 → CO2 + 2H2 O
Native Form
Chemical Compound
2
a. 2K
+ 2H2 O → 2KOH + H2
b. 4C2 H5 OH
+ 11O2 → 8CO2 +
10H2 O
c. Cl2
e. F e2 O3
Product
Kinetic Theory
+ 2KI → 2KCl + I2
d. 4CrO3
Reactant
→ 2Cr2 O3 + 3O2
+ 3C → 3CO + 2F e
Mixtures
homogeneous
heterogeneous
Inter-particle forces
Sublimation, Deposition,
Evaporation, Boiling Point
Chapter 1 Stoichiometric Relationships
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1.2
Avogadro's number:
6.02214129 ⋅ 1023
Relative Atomic Mass is
compared to the C12 element
n=
m
MM
Empirical formula gives the
simplest form of the formula but
not how the actual bonding is
Molecular formula gives the
actual bonding in a substance
Hydrated and anhydrous salts
are salts that have water crystals
and that do not have water
crystals respectively
Percentage by mass gives the
percentage of a substance an
element holds up and with this
information the amount of moles
in that substance, its empirical
formula and its molecular
formula can be fond.
1.3
The combined gas law: for a
fixed mass of gas: PT1 V1 = PT2 V2
1
Chapter 1 Stoichiometric Relationships
2
3
• The ideal gas equation: PV =
nRT
• R = 8.31 J K1 mol–1, T must be
in K.
• Temperature (in K is a
measure of the average kinetic
energy of the particles. Particles
have minimum kinetic
energy at absolute zero 0 K.
• As kinetic energy = ½mv2 and
all gases have the same kinetic
energy at the same temperature,
particles with
smaller mass move faster.
• Avogadro’s law states that
equal volumes of different gases
contain equal numbers of
particles at the same
temperature and pressure.
• Number of mol = volume/molar
volume = V/Vmol
• Molar volume, Vm, of any gas
at STP = 2.27 × 102 m3 mol–1.
• STP for gases is standard
temperature 0 °C or 273 K and
pressure 100 kPa).
• Density = mass/volume; ρ =
m/V
• A solution is a homogeneous
mixture of a liquid (the solvent)
with another substance (the
solute). The solute
can be solid, liquid, or gas but
the solvent is generally a liquid.
• Concentration is the amount of
solute in a known volume of
solution. It can be expressed
either in g dm–3 or
mol dm–3. Concentration in mol
Chapter 1 Stoichiometric Relationships
4
dm−3 is often represented by
square brackets around the
substance:
[solute] (mol dm−3 = nsolute
(mol)/Vsolution (dm3) nsolute =
[solute] × Vsolution (dm3)
nsolute = [solute] × Vsolution
(cm3)/1000
• Titration is a chemical
technique in which one solution
is used to analyse another
solution to find its
concentration or amount.
Notes Column
💡
Key Concepts
Physical and chemical properties depend on the ways in
which different atoms combine
The mole makes it possible to correlate the number of
particles with a mass that can be measured
Mole ratios in chemical equations can be used to calculate
reacting ratios by mass and gas volume
1.1 Introduction to the particulate nature of matter
and chemical change
Combustion is the burning of a substance with oxygen
Chapter 1 Stoichiometric Relationships
5
A Chemical element is a single pure substance made of only one type of atom
Each element has a symbol
Single Upper Case
or
Two letters, first upper case second lower case
The native form of a substance is the substance without in any combination
with other elements in nature
Chemical Compound is a combination of elements
Chemical Equations Summarize Chemical Change
A Chemical Change is the formation of compounds from elements and is
represented by a chemical equation
Chemical equation is the representation of chemical compounds
Reactants are on the left side of the equation
Products are on the right side of the equation
The amount of atoms on the reactant side are equal to the ones on the products
side
Stoichiometric coefficients are the numbers in front of each term being used
that indicate the amount
A chemical equation always has to be balanced
'Heating' and 'thermal decomposition' do not mean that the oxygen is the
reactant, but that the heat is the source of energy. 'Burning' and 'Combustion',
however, do represent that oxygen is a reactant
Chapter 1 Stoichiometric Relationships
6
Atom Economy is the efficiency of the reaction and it shows the percentage of
useful products compared to the waste.
Mass Of Desired P roduct
⋅ 100
T otal Mass Of P roducts
💡
Total Mass of Products represents the 'mass of desired product' + the
waste product that is produced. For example: breaking down glucose
with oxygen to obtain carbon dioxide (cellular respiration) but this
reaction also gives us water, which would be the waste in this case. So
the mass of desired product {CO2 } is less than the total mass of the
products {CO2
+ H2 O
Mixtures form when substances combine without chemical
reaction
A mixture is a combination of different elements and compounds that have no
chemical reaction between them.
Their composition is not fixed (air we inhale is 20% oxygen while the air we
breathe out is 16% oxygen, but we both call them air) The proportion of the
components in a mixture doesn't matter
A homogeneous mixture is one where the components are uniform in
composition and their properties. They blend in)
A heterogeneous mixture is one where the properties aren't the same and one
can usually see the difference Oil and water)
Matter exists in different states determined by the temperature
and the pressure
Chapter 1 Stoichiometric Relationships
7
The state of the matter (liquid, solid, gas) depend on the pressure and
temperature they are being subjected to.
The kinetic theory states that the average kinetic energy of the particles are
directly proportional to the absolute temperature of the system.
1
mv2 ∝ K
2
The inter-particle forces, strength of the forces that exists between the
particles, defines the state of the matter
Fluids are gases and liquids
Diffusion is the process in which substances are evenly distributed
Chapter 1 Stoichiometric Relationships
8
When writing chemical equations, always use state symbols to determine which
state the reactants and products are in.
Matter Changes State Reversibly
State changes are caused due to the particles overcoming the inter-particle
forces
Sublimation is the direct change of solid to gas
Deposition is the direct change of gas to solid
Evaporation happens only at the surface while boiling happens as a whole
The graph of change of state is shown as seen below:
Chapter 1 Stoichiometric Relationships
9
Quick Summary
State of matter changes according to temperature and pressure.
When writing equations always write the state symbols (s), (l), (g)
The kinetic energy of the molecules depend on the absolute temperature, and
they are directly proportional to it.
Inter-particle forces keep the substances in a certain state
1.2 The Mole Concept
The Avogadro constant defines the mole as the unit of amount
in chemistry
Chapter 1 Stoichiometric Relationships
10
1 mole is equal to
6.02214129 ⋅ 1023 of any substance
1 mole gives you the gram value of the elements that they had in amu. So, if an
atom of an element had a mass of 10 amu, one mole of that element would give
you 10 grams.
Conversion factor:
Avagodro ′ s N umber
amu
= 1 mole
Relative Atomic Mass is Used to Compare the Masses of Atoms
Isotopes are the same element with different masses due to a change in the
amount of neutrons in the nucleus
Weighted Average is the average of the masses of the isotopes and the
concentration of them in an environment
Relative Atomic Mass
Ar :
W eighted average of one atom of the element
1
mass of one atom of carbon − 12
12
Molar Mass is the Mass of one mole of a substance
Molar Mass is the mass of one mole of substance which is the same value in
grams instead of amu
Notations used for the following are:
n - number of moles
m - mass in grams
n=
m
M
M - molar mass
Chapter 1 Stoichiometric Relationships
11
The Empirical Formula of a Compound Gives the Simplest Ratio
of its Atoms
The ratio of moles is the same as the ratio of atoms between two substances
The empirical formula gives the simplest whole number ratio of the elements in
a compound
It doesn't show how the elements bond nor does it represent the true
amount)
Hydrated Salts are salts that contain water molecules which are called water of
crystallization
Anhydrous salts which do not contain crystallized water
One can find the empirical formula of a substance from the percentage mass
that is given. To do this take the mass as grams and divide it by the molar mass
for each element. After this you will have the amount of moles for each
substance. Take the smallest and amount and make it 1, then multiply the rest by
that number. You will get the necessary numbers to do the rest.
Percentage Composition by Mass can be calculated from the
empirical formula
To find the percentage by mass in a substance, just divide the mass of the
specific element by the molar mass of that substance.
The percentage by mass does depend on the relative mass of each element.
The Molecular Formula of a Compound Gives the Actual Number
of Moles in a Molecule
Chapter 1 Stoichiometric Relationships
12
A molecular formula is the way in which the formula shows how the elements
are combined depending on their number. As you can recall empirical formula
doesn't represent how the substance is found in real life. It is just the simplified
form
Molecular
x(mass of emprical formula) = MM, where x is an integer
formula:
Combustion Analysis Usually Gives Data on The Mass of
Compounds Formed
Look through this again)
Quick Summary
Avogadro's number: 6.02214129
⋅ 1023
Relative Atomic Mass is compared to the C12 element
n=
m
MM
Empirical formula gives the simplest form of the formula but not how the actual
bonding is
Molecular formula gives the actual bonding in a substance
Hydrated and anhydrous salts are salts that have water crystals and that do not
have water crystals respectively
Chapter 1 Stoichiometric Relationships
13
Percentage by mass gives the percentage of a substance an element holds up
and with this information the amount of moles in that substance, its empirical
formula and its molecular formula can be fond.
1.3 Reacting Masses and Volumes
Chemical Equations Show Reactants Combining in a Fixed Molar
Ratio
Chemical changes are represented by chemical equations, and in these
equations the amount is represented by ratios. These ratios can be seen as
moles per substance and then be balanced out later.
The Theoretical Yield is Determined by the Limiting Reactant
The limiting reactant is the one that determines the quantity of product that will
be produced from an equation. Usually it is the one with less moles than the
balanced ratio)
Other reactants, the ones that aren't limiting reactants, are called excess.
If 100% of the reactants actually react with each other, we get the product
called the theoretical yield. It is theoretical because almost 100% of the time
not all reactants react to produce that product
Chapter 1 Stoichiometric Relationships
14
The Percentage Yield Can Be Calculated From the Experimental
and Theoretical Yields
Experimental yield is the actual amount of product that we get in real life
Percentage yield represents this
by this formula:
experimental yield
⋅ 100%
theoretical yield
Avogadro's Law Directly Relates Gas Volumes to Moles
Gas volume is only determined by the amount of particles it has, and the
temperature & pressure it has been subjected to
The law states this:
Equal volumes of all gases, when measured at the same
temperature and pressure, contain an equal number of
particles
The converse of this law (equal number of particles under constant temperature
and pressure have the same volume) is also true
All Gases Under the Same Conditions Have the Same Molar
Volume
Chapter 1 Stoichiometric Relationships
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no of moles =
volume(V )
molar volume
Volume of gas at STP 0°C and 100kPa {not 1 atm}) is
22.7 dm3
mol
A note about the units of volume
The Gas Laws Describe Pressure, Volume, and Temperature
Relationships for All Gases
Chapter 1 Stoichiometric Relationships
16
An Ideal Gas is one where it has negligible volume with no inter-particle forces.
It also doesn't solidify at 0K
A Notes About Units of Temperature
At the temperature of 0K, the kinetic energy of particles is zero.
1K = 1°C + 273.15
A Note About Units of Pressure
1 bar = 105 Pa
N
Pa Pascal) is equal to m2
1 bar = 0.986923 atm
1. Relationship Between Volume and Pressure
Volume of gas is always volume of its container
Chapter 1 Stoichiometric Relationships
17
P∝
1
V
2. Relationship between Volume and Temperature
V ∝T
T is in Kelvin
Also known as Charles' Law)
Chapter 1 Stoichiometric Relationships
18
3. Relationship Between Pressure and Temperature
P ∝T
The Ideal Gas Equation is Derived from the Combined Gas
Equation and Avogadro's Law
⁍
N ⋅m
J
Value of R 8.31 K ⋅mol or 8.31 K ⋅mol This is when the pressure is given in
pascals, not atm)
Value of R in atm: 0.082
Real gases show deviation from ideal behavior
Ideal gases obey the P V
= nRT rule at all times, but not real gases.
Real gases deviate from ideal behavior at high pressure and low temperature
Chapter 1 Stoichiometric Relationships
19
The concentration of a solution depends on moles of solute and
volume of solution
Solutions contain two or more components
Solvent is the component present in the greatest quantity
Solute is the one that dissolves
Concentration is the amount of solute in a volume of a solution (not solvent)
Equation is c
=
n
V
Concentration is usually expressed with the term molarity
g
mol
Other representation are: dm
3 and dm3 (these will most likely be used in
IB
PPM (also known as parts per million) shows the part per 106 by mass (used in
very low concentrations
mass of component
total mass of solution
⋅ 106
Dilutions of Solutions Reduce the Concentration
Stock solution is a more concentrated starting solution which is obtained by
adding more solvent.
As a solution becomes diluted: c1 V1
Chapter 1 Stoichiometric Relationships
= c2 V2
20
The Concentration of a Solution Can be Determined by
Volumetric Analysis
Equivalence Point is the point at which two solutions have completely reacted
Titration
Chapter 1 Stoichiometric Relationships
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