By: Hilary Megeney
& Kristen Jorgensen
Chemistry 11 adv
Mole conversions
volume
STP: 22.4 L
NTP: 24.4 L
SATP: 24.8 L
moles
6.02 x 10²³
g/mol
mass
atoms/molecules
Pv = nRT
P - pressure in kPa
v - volume in liters (L)
n - number of moles
R - the universal constant of gases (8.31)
T - temperature in K
Empirical/Molecular Formula
An empirical formula give the lowest whole number ratio of the
elements in a compound.
Take the percentage composition given of each element and
then divide by their atomic mass. This gives you the number of
moles. Divide all the numbers by the lowest number of moles.
This gives you the amount of element in the compound.
Coefficients
N2 + 3H2 → 2NH3
The number in front is called the
coefficient; it gives us the mole ratio. The
example above has a 1:3:2 ratio.
Anhydrated and Hydrated
Compounds
An anhydrated compound does not have
any water in it. It is dry. A hydrated
compound has water added to it.
Stoichiometry
Grams to Moles
1.
Write down the balanced equation of the reaction.
2.
Then use the given number of grams to calculate moles, using the
factor label.
Grams to Grams
1.
Write down the balanced equation of the reaction.
2.
Use the given number of grams as the starting value for factor label.
3.
Then convert to the number of moles of that element.
4.
Use the mole to mole ratio to convert in terms of the element you are
solving for.
5.
Convert the moles into grams by multiplying by atomic mass.
Limited and Excessive Reactant
When you’re given a balanced equation a precise amount of each
reactant is needed, similar to a recipe. When you do an experiment
you only have a limited supply of each compound. Your limited
reactant is the compound that you run out of first. You excessive
reactant is the compound you have left over.
Defining the
mole
Gases
Factor Label
Limited and
Excessive
Percentages
100
100
100
100
100
200
200
200
200
200
400
400
400
400
400
600
600
600
600
600
800
800
800
800
800
1000
1000
1000
1000
1000
What is Avogadro’s number?
6.02 x 1023 particles
How many atoms are present in
1.75 mole of calcium?
1.0535 x 1024
1 mole = ? in grams
(Hint: It’s unit is g/mol)
1 mole = molar mass in grams
What’s the cookie analogy?
3F + 2S = 12C
What is the molar mass in a
compound?
The molar mass in a compound is
the sum of all the masses of all the
elements.
What is the molar mass of an
element?
The molar mass of an element
is the number of grams of the
element that is equivalent to it’s
atomic mass.
What is the volume of gases
measured at standard ambient
temperature and pressure?
24.8 L
What is the volume of 0.505 mole
NH3 gas at SATP?
12.524 L
What are the units for Pv=nRT?
•
•
•
•
Pressure – kPa
Volume – L
Constant – 8.31
Temperature – K
What is the volume of 2.8 grams of
CO2 (g) at SATP
1.578 L
What is the formula for the ideal
gas law? *(in words)*
Pressure · volume = number of
moles · constant · temperature
How many litres of CO2 are
produced? If 20 L of O2 are
consumed at NTP, using the
equation below.
C3H8 + 5O2 → 3CO2 + 4H2O
12 L of CO2
How many moles
H2 of are produced,
given the balanced
equation:
N2 + 3H2 → 2NH3
1.71 mol of H2
3.45g H2 x 1 mol H2 = 1.71 mol of H2
2.02g H2
How many steps
are in a mass to
mass problem?
(factor label)
3
How many grams
of NH3 are
produced, given
the balanced
equation:
N2 + 3H2 → 2NH3
19.4 g NH3
3.45g H2 x 1 mol H2 x 2 mol NH3 x 17.04gNH3 = 19.4g NH3
2.02g H2 3 mol H2
1 mol NH3
How many grams
of H2(g) will be
needed to react
with 50.0g of N2(g)
in the following
reaction?
N2(g) + 3H2(g) → 2NH3
10.82 grams H2
50 g H2 x 1 mol N2 x 3 mol H2 x 2.02 g H2 = 10.82 g H2
28 g N2
1 mol N2
1 mol H2
What is the mass of
potassium chloride
formed when 24.5 g
of potassium
chlorate decompose.
Use the balanced
equation:
2KClO3 → 2KCl + 3O2
14.9 g KCl
14 g H2 x 1 mol KClO3 x 2 mol KCl x 74.55 g KCl = 14.9 g KCl
122.55 g KClO3
1 mol KClO3
1 mol KCl
Potassium reacts with
water to give
potassium hydroxide
and dihydrogen.
Determine the mass of
water decomposed
during this reaction, if
there is 14 g of H2.
249.5 g H2O
2K + 2H2O → 2KOH + H2
14 g H2 x 1 mol H2 x 2 mol H2O x 18 g H2O = 249.5 g H2O
2.02 g H2
1 mol H2
1 mol H2O
Define the limiting
reactant?
The element that is
used up first
Define the excessive
reactant?
The element that is
left over after the
reaction.
0.486g of magnesium
react with 0.1 moles
of dioxygen to form
magnesium oxide.
2Mg + O2 → 2MgO
Magnesium: Limited
Oxygen: Excessive
0.486gMg = 0.0101
48g
limited
0.1mol02 = 0.1
1mol
excessive
Identify the limited
and excessive
reactant if 1g of NH3
is mixed with 1 g HCl,
using the following
balanced equation.
NH3(g) + HCl(g) → NH4Cl(g)
NH3 – excessive
HCl - limiting
NH3
1
= 0.05868
17.04
HCl
1
= 0.02743
36.46
Chlorine dioxide, ClO2, has
been used as a disinfectant
in air-conditioning systems.
It reacts with water
according to the following
equation. If 142.0 g of ClO2
is mixed with 38.0 g of H2O,
how many grams of which
reactant remain if the
reaction is complete?
6ClO2 + 3H2O → 5HClO3 + HCl
19.0371 g of H2O in
excess
142 g ClO2
404.7108
= 0.35087
(limited)
38 g H2O
54.04584
= 0.78107
(excessive)
142 g ClO2 x 1 mol ClO2 x 3 mol H2O x 18.01528 g H2O = 18.9629
67.4518 g ClO2 6 mol ClO2
1 mol H2O
38 – 18.9629 = 19.0371
Fill in the blanks using this equation:
C2H4 + H2O → C2H5OH
What happens if we mix three molecules of
ethylene with 5 molecule of water? The _______
will be completely used up before all of the
_______ is, and the product will contain _______
molecules.
In this reaction mixture ethylene is called the
______ reactant, because it ______ the amount of
product formed, and water is called the ______
reactant, because there will be _______________
HINT: you can use your textbook.
What happens if we mix three molecules of
ethylene with 5 molecule of water? The ethylene
will be completely used up before all of the water
is, and the product will contain 2 unreacted water
molecules.
In this reaction mixture ethylene is called the
limited reactant, because it limits the amount of
product formed, and water is called the excessive
reactant, because there will be water molecules
left over.
What is percent composition?
The amount of each element by
mass that makes up a compound,
for a total of 100%
What is the percent composition of
the compound H2CO3?
• % of H = 2.6 %
• % of C = 15.4 %
• % of O = 82.1%
Find the empirical formula of the
compound, given the mass in
percentage composition: 9.93% of
carbon, 58.6 % of chlorine, and
31.4% of fluorine.
CCl2F2
C = 9.93 = 0.83
Cl = 58.6 = 1.65
12.01
35.45
0.83/0.83 = 1
1.65/0.83 = 2
F = 31.4 = 1.65
19
1.65/0.83 = 2
If we mix together 28.2 grams of
salicylic acid with 15.6 grams of acetic
anhydride in this reaction we obtain
30.7 grams of aspirin. What is the
percentage yield?
In the synthesis of aspirin we react
salicylic acid with acetic anhydride.
83.5% yield
Salicylic acid: 28.2
= 0.1021 (limited)
276.26
Acetic anhydride: 15.6 = 1.528 (excessive)
10.21
28.2 g SA x 1 mol SA x 2 mol ASA x 180.17 ASA = 36.78 g ASA
138.13 g SA
2 mol SA
1 mol ASA
theoretical
Actual:
Theoretical:
30.7 g
= 83.5%
36.78 g
Define Percentage Yield
The amount of product obtained
in a chemical reaction
What is the difference between
Empirical formula and Molecular
formula?
Empirical Formula represents the
most simple ration between the
elements.