Thursday
January 31, 2013
(Mass to Mole
Stoichiometry)
Bell Ringer
Thursday, 1-31-13
If 5.0 moles of mercury (II) oxide decompose, how
many grams of mercury will be produced?
2 HgO æ 2Hg + O2
5.0 mol
5.0 mol HgO
1
X
? grams
mol Hg
mol HgO
X
g Hg
mol Hg
= 1005
g Hg
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Announcements
I will be available after
school today until 4:45.
Assignment
Currently Open
Summative
or
Formative?
Date
Issued
Date Due
Date Into
GradeSpeed
Final Day
QUIZ 16
S1
1/18
1/18
1/24
2/7
WS - Introduction
to Stoichiometry
and Mole Ratios
F7
1/23
2/1
TOMORROW
WS – Review of
Molar Mass
F8
1/24
2/1
TOMORROW
Project Share Quiz
– Reactions and
Balancing
F9
1/25
1/25
TOMORROW
WS – Mole to
Mole
Stoichiometry
F10
1/29
2/1
TOMORROW
WS – Mole to
Mass
Stoichiometry
F11
1/30
2/1
2/8
Types of Stoichiometry Problems
Mass – Mole Conversions : Given is a
mass in grams and the unknown is an
amount in moles.
When you are given the mass of one substance
and asked to calculate the amount in moles of
another substance in the chemical reaction, the
general plan is:
Converting Mass to Moles
The following is a solution plan for problems in which
the given quantity is expressed in grams and the
unknown quantity is expressed in moles.
Converting Mass to Moles
Sample Problem
The first step in the industrial
manufacture of nitric acid is the catalytic
oxidation of ammonia:
NH3 + O2 → NO + H2O (unbalanced)
The reaction is run using 824 g of NH3
and excess oxygen.
a. How many moles of NO are formed?
b. How many moles of H2O are formed?
Converting Mass to Moles
Sample Problem
The first step in the industrial manufacture of nitric acid is the
catalytic oxidation of ammonia:
NH3 + O2 → NO + H2O (unbalanced)
The reaction is run using 824 g of NH3 and excess oxygen.
a. How many moles of NO are formed?
b. How many moles of H2O are formed?
Given: mass of NH3 = 824 g
Unknown: a. amt. of NO produced (in mol)
b. amt. of H2O produced (in mol)
Converting Mass to Moles
Sample Problem
The first step in the industrial manufacture of nitric acid is the
catalytic oxidation of ammonia:
NH3 + O2 → NO + H2O (unbalanced)
The reaction is run using 824 g of NH3 and excess oxygen.
a. How many moles of NO are formed?
b. How many moles of H2O are formed?
Start with a balanced equation:
4NH3 + 5O2 → 4NO + 6H2O
Converting Mass to Moles
Two conversion factors are needed to solve part (a) - the molar
mass of NH3 and the mole ratio of NO to NH3.
Part (b) starts with the same conversion factor as part (a), but then
the mole ratio of H2O to NH3 is used to convert to the amount in
moles of H2O. The first conversion factor in each part is the
inverted molar mass of NH3.
Converting Mass to Moles
Use the periodic table to compute the molar mass of
NH3.