Transcript Naming compounds, moles et

Chemical Symbols - Each element has a one, two
or three letter symbol to
represent it
- Symbols with more than one letter are
always written capital letter then lower case
letter
- Based on IUPAC system of naming
Diatomic molecules - elements found only combined
covalently in nature
H2, N2, O2, F2, Cl2, Br2, I2
Element vs. Compound
Element - Atoms of all the same type
Cannot be chemically broken down into two
different substances. Na Cu
Compound
Combination of elements NaCl
CuSO4
a. All sample of a compound have the
same properties
b. Atoms in a compound are in a simple
ratio
c. All areas of a compound are the same
What’s in a Quarter?
What two elements do you think are found in a quarter?
(Write the name an symbol below.
What do you think will happen when the RED HOT
quarter is placed into the beaker of methanol?
Describe what did happen?
Is the reaction that took place exo or endothermic/
Why did the quarter change color?
Chemical formulas tell us two things
Type of elements present
Number of atoms
Subscript- Indicates number of atoms
Examples
MgBr2
1 Mg for every 2 bromines
Al2O3
2 aluminums for every 3 oxygens
Ca(OH)2 1 calcium , 2 hydrogens and 2 oxygens
2 sets of OH
Example - How many sulfur atoms are present in Pb(SO4)2?
2
4x2=8
How many oxygen atoms are present?
Coefficients -numbers placed in front of a chemical
formula to indicate how many
molecules are present
MgS
Ex.
MgS
6 MgS
MgS
MgS
MgS
MgS
Burning Money!!!!
Examine the following equation and answer the questions that follow
2 C3H7OH(l) + 9 O2(g) → 6 CO2(g) + 8 H2O(g)
∆Hrxn = -1987 kJ/mol
What is the total number of molecules in this
equation?
How many atoms of oxygen are in the equation?
Describe the reaction as either exothermic or
endothermic.
Hydrates - Water gets trapped in the crystal structure
of some ionic compounds
-The same amount of water is found in the
crystal all the time
Ex. CuSO4* 5H2O
* Does not mean multiply!!! It means it is an hydrate!
Types of Chemical Formulas
Molecular Formula
Tells us how many atoms of each element are
needed to form the molecule
Examples C2H6 -ethane - 2 C : 6H
Empirical Formula
Shows the simplest ratio of atoms
C2H6
Molecular
C3H6
CH3
Empirical
CH2
Sometimes the empirical formula and the molecular
formula are the same
CO
HO
2
2
Which of the following are empirical formulas?
A. H2O2
B. CO
C. P2O4
D. Al2O3
What is the empirical formula of the following?
C6H12O6
Hg2O4
CH2O
HgO2
PbSO4
PbSO4
Writing Chemical Formulas
When Ba is combined with Cl, is the formula BaCl?
Or ClBa?
Or Cl2Ba?
Based on OXIDATION NUMBERS
Or Ba2Cl?
Oxidation numbers -Indicate the number of electrons lost or
gained in a bond
Oxidation number
Negative oxidation number
Atom gains partial or
total control of electrons
Positive oxidation number
Atom loses partial or
total control of electrons
1. The element or ion with the positive oxidation state
(the metal) is written first
Write in the
oxidation
states, then
write out who
comes first.
Written
first
Mg
Cl
O
Li
+2
-1
-2
+1
Br
Ca
Cu
S
-1
+2
+?
-2
Mg
Ca
Cu
Li
Written
second
Br
Cl
O
S
2. The oxidation states of all elements in a compound must
add up to zero
-For every electron lost, it must be gained by another atom
Example
Ca+2
Cl
-1
Cl
-1
CaCl2
Loses control of 2 e- Gains control of 1e2 eAdd one more Cl-1 to get to zero
+1
H
O -2
Li
+1
S
H2O
-2
Li2S
3. Polyatomic ions are treated as one element
Ca +2
SO4 -2
CaSO4
Na
+1
PO4
-3
Na3PO4
4. If a polyatomic ion is used more than once, put
parentheses around it
+2
-1
Ca(OH)2
Ca
OH
NH4
Practice
+1
SO3
Lithium oxide
Magnesium iodide
-2
Li+1
Mg+2
potassium phosphate K+1
(NH4)2SO3
O-2
Li2O
I-
MgI2
PO4-3
K3PO4
NH4NO3
ammonium nitrate
NH4+
NO3-
aluminum oxide
Al+3
O-2
+2
Ca
calcium phosphate
PO4-3
Al2O3
Ca3(PO4)2
Nomenclature
Naming compounds
1. Binary Compound Consists of 2 different elements
To name these, use the name of the first atom, remove “ine”
from the second atom and add “IDE”
NaCl
Na__________
Cl_________
NaCl _____________________
You must know the –ide names for the following
Hydrogen
Hydride
Oxygen
Oxide
Bromine
Bromide
Iodine
Iodide
Fluorine
Flouride
Nitrogen
Nitride
Selenium
Selenide
Sulfur
Sulfide
Examples
Magnesium bromide
bromine LiO Lithium oxide
MgBr2 Magnesium
SrO Strontium oxygen
AlI3 Aluminum iodide
oxide
NaF Sodium fluoride
ZnS Zinc sulfide
2. Ternary compounds
Compounds with 3 or more elements
-usually a metal with a
POLYATOMIC ION
Polyatomic ion
O
|
O-P-O
|
O
-3
Group of atoms bonded together to obtain
an overall charge
Has special properties unlike the individual
atoms
Often acts as one atom
Found on Table E
PO4-3 phosphate
Name the following polyatomic ions
+
-2
NH
-2
4
SO3
OH
CO3
sulfite
hydroxide
carbonate ammonium
Polyatomic ions bond IONICALLY with other ions
Naming compounds with polyatomic ions
- Do not change any parts, take the name of each part
of the compound
-Circle the polyatomic ion in each compound, then name the
compound
MgSO4
LiOH
CaCO3
Al(OH)3
Magnesium sulfate
Lithium hydroxide
Calcium carbonate
Aluminum hydroxide
NaSCN
Sodium thiocyanate
NH4OH Ammonium hydroxide
Li2SO3 Lithium sulfite
Naming Covalent Compounds
-compounds with only nonmetals
-using Table S, write the name of the element with the
lower electronegativity first
-use prefixes to tell how many of each element are
present
Ex.
2.6
CO2
3.4
N2Cl2
3.0
3.2
Carbon dioxide
2 oxygen's
Dinitrogen dichloride
Try: Carbon tetrachloride
Diphosphorous pentoxide
Name the following Compounds
LiBr
MgSO4
CaCO3
SrCrO4
ZnS
Al2(SO4)3
NH4NO3
Write the empirical formula
C2H2
PbCl4
H2O2
C6H12O6
P2O4
Write out the following formulas
Calcium oxide
Lithium Sulfide
Lithium Sulfate
Magnesium phosphate
Aluminum carbonate
Nitrogen dioxide
So far, we have learned how to take different
elements and combine them together to make a
compound.
But there are some elements that have several
oxidation states.
For example, what is the formula for lead oxide?
Pb has two oxidation states Pb+2 and Pb +4
Pb+2 O-2
PbO
Which of the two is correct?
Pb+4 O-2
O-2
PbO2
BOTH are correct!
How can we have two different formulas with the
same name?
We need a way to distinguish between these two.
- used when the first part of a compound (the positive one)
has two or more positive oxidation states.
Which of the following requires the stock system?
CuO
MgO
Yes
NO
Yes
NO
CaSO4
NO
LiNO3
NO
Ni(NO3)2
Yes
ZnCO3
NO
How is the stock system used?
1. Assign oxidation numbers to the elements in the compound
2. Write the oxidation state of first element as a roman numeral
+4 O-2
Pb
Pb+2 O-2
O-2
PbO
PbO2
Pb is in the +2 state, so it is called
Pb is in the +4; state, so it is called
Lead (II) oxide
Lead (IV) oxide
+2 -1
SnCl2 Sn has an oxidation state of +2 or +4.
+2 -2 = 0
The Cl must be in the -1 state, since Sn must be a positive
oxidation state,
Since there are two Cl’s, the Sn must be in the +2 oxidation
state to cancel out the Cl’s
Tin (II) Chloride
Practice - All of the following compounds need the stock
system. Determine the oxidation state of the cation (the
first ion) and write out the name.
+1
-1
CuNO3
+2 -1
NiF2
+2 -2
+2 -2
HgO
+1 -2
Hg2O
+2
Copper (I) nitrate
Nickel (II) fluoride
Mercury (II) oxide
Mercury (I) oxide
-2
+3 -1
FeCl3
+3 -3
+4
-2
NO2
+4
-4
Iron (III) chloride
Nitrogen (IV) oxide
If we are given a chemical name that uses the stock
system, how do we write the formula?
Example - What is the chemical formula for
Copper (II) oxide?
We know that the compound contains copper and oxygen
And we know that oxygen must take a -2 oxidation state
-2
+2
Cu O
Don’t have to look up copper. The (II) tells us
that it is in the +2 state
What is the chemical formula for copper (II) oxide?
CuO
What is the formula for Nickel (III) sulfate?
+3
Ni
-2 According to chart E!
SO4
Ni2(SO4)3
Now write out the formulas for the following.
Nitrogen (II) chloride
N+2
Cl-1
NCl2
Iron (III) oxide
Fe+3 O-2
Lead (IV) carbonate
Pb+4 CO3-2 Pb(CO3)2
Copper (I) sulfate
Cu+1 SO4-2 Cu2SO4
Fe2O3
- Shows what happens during a chemical reaction
The chemicals involved
How many of each molecule
Energy used, phases
Reactants Substances that exist before the reaction takes place
Always found on the left, or facing away from the arrow
Products
Substances that exist after a chemical reaction
Always found on the right, or facing the arrow head
The reaction arrow is the “
“. It is always found in
the middle of a chemical reaction and it divides up the
reactants and the products
Examples - List the reactant and the products of the following
reactions
Reactants
Products
a. 2 H2 + O2
b. HCl + NaOH
2 H2O
2 H2
H2O + NaCl HCl
O2
NaOH
2 H2O
H2O NaCl
Balancing a chemical equation
CO + O2
CO2
How many carbon atoms are on each side of the equation?
1
How many oxygens are on each side of the equation?
Three on the reactants, but only 2 one the products side
Is this possible?
No, something must happen to the
=
O = C=O
O
other oxygen
O O
O O O
?
We need another CO for the other oxygen to attach to.
= O So two molecules of CO combine with
O = C=O
O
O O
one molecule of O2
O
O O
O
O = C=O
2 CO + O2
2 CO2
O
2C 4O
2C 4O
O
Now the equation is balanced because we have the same
number and types of atoms on both sides
Problem 1: Write the balanced equation for the reaction between
aluminum sulfate and calcium chloride to produce aluminum
chloride and a white precipitate of calcium sulfate.
Step 1: Write the word equation
Aluminum sulfate + Calcium chloride  Aluminum chloride + Calcium Sulfate
Step 2: Replace the words with the correct formulas
Al2(SO4)3
+
CaCl2 
AlCl3
CaSO4
+
Step 3: Adjust coefficients to make the equation balance. Use
trial and error until both sides have same number of each
element.
Al2(SO4)3
+
CaCl2 
AlCl3
+
CaSO4
This is a hit and miss procedure. Often you will need to
change the coefficients several times in order to balance
the equation correctly
Remember to only change the coefficients, not the
molecular formula
Examples
2
a. ____ NH3
3
_____ N2 + ____ H2
2
b. ____ Li2SO4 + ____ Na
2
c. ____ HCl + ____ Mg
2
____ Na2SO4 + ____ Li
____MgCl2 + _____ H2
-Some pure elements must exist as
DIATOMIC molecules
H
Pure hydrogen gas is H2
N
Pure nitrogen is N2
This occurs for the following elements
H, N, O, F, Cl, Br, I
Example - Balance the following equation
Nitrogen + oxygen
N2 + O2
2 NO
nitrogen (II) oxide
Showing Energy changes in Reactions
A. Reactions that require energy are endothermic
Ex. 2 H2O + energy  2 H2 + O2
B. Reactions that give off energy are exothermic
Ex. 2 H2 + O2  2 H2O + energy
Match-Making
The first matches were invented in 1827 by chemist John
Walker. He determined that a wood splint tipped with antimony
(II) sulfide, potassium chlorate, gum and starch could be
ignited by striking it against a rough surface.
Write the formulas for the following compounds
Antimony (II) sulfide
Potassium chlorate
Describe the reaction that took place when Mr. Stone
lite the mixture on fire.
Was the reaction exo or endothermic and explain why.
Why safety matches? Combustible materials are separated
between match and striking surface
Balance the following equations
•_____ KNO3 + _____ Na2SO4  _____ K2SO4 + _____ NaNO3
•_____ H2 + _____ Cl2  _____ HCl
•_____ Li + _____ O2  _____ Li2O
•_____ HgO  _____ Hg + _____ O2
•_____ AlBr3 + _____ Cl2  _____ AlCl3 + _____ Br2
•Nitrogen + oxygen  nitrogen(IV) oxide
•Barium chloride + sodium sulfate  barium sulfate + sodium chloride
•Magnesium + sulfuric acid  magnesium sulfate + hydrogen gas
•Potassium + water  potassium hydroxide + hydrogen gas
Aluminum + hydrochloric acid  aluminum chloride + hydrogen gas
There are four basic types of chemical reactions
Observe the products and the reactants to determine the type of
reaction.
A. Synthesis
Two or more compounds combine together to produce one
compound
Ex. A + B --> AB
Examples
2 H2 + O2 --> 2 H2O
2 Mg + O2 --> 2 MgO
Exothermic reaction of Calcium oxide and water
B. Decomposition
Single compound breaks down into 2 or more compounds
AB --> A + B Examples
2 H2O --> 2 H2 + O2
2 NaCl --> 2 Na + Cl2
C. Single Replacement
Element + Ionic Compound
Element + Ionic Compound
X + AB  A + XB
Ex. Zn + CuSO4  ZnSO4 + Cu
What does an elephant use to clean it’s teeth?
Elephant toothpaste
Balance the equation below
H2O2(aq) →
H2O(g) + O2(g) + energy
What if the name of the H2O2 (you’ll need to use table E)
We’ve talked of many types of reactions at this
point. Use to types that we’ve talked about during
this unit to describe the reaction above.
D. Double Replacement
2 compounds in solution are mixed
CC C
Ex.
C
AB
CA D
A AA
AB + CD --> CB + AD
Watch the oxidation states when making new compounds!
NaCl(aq) + AgNO3(aq)
AlI3 + 3 NaOH
NaNO3(aq) + AgCl(s)
Al(OH)3 + 3 NaI
Synthesis reaction –
fog machine
Synthsis pg 113
Pg 117 synthesis
Single and double replacement
123
Elephant toothpaste decomp
Unknown Reactants and Products
-since matter can NOT be created or destroyed, you
must always have the same number of each type of
element on each side of the equation
-if you have a balanced equation you should be able
to figure out what the unknown product or reactant
is
EX. H2SO4 + 2 NaOH  Na2SO4 +
WHAT?
BaCl2 + K2CO3  WHAT? + BaCO3
2 NaHCO3  Na2CO3 + H2O + WHAT?
Determining Missing Mass in an Equation
RULE: Total mass of reactants = total mass of products
If 103.0g of KClO3 are decomposed to form 62.7 g of
KCl and O2 gas according to the equation
2 KClO3  2 KCl + 3 O2
How many grams of oxygen are formed?
Total mass of reactants = 103.0 g
Total mass of products = 103.0 g
103.0 = mass of O2 + 62.7 g KCl
103.0 – 62.7g KCl = mass of O2
How many grams of silver nitrate are needed to react
with 156.2g sodium sulfide to produce 595.8 g silver
sulfide and 340.0 g sodium nitrate?
1. Rewrite and balance the equation.
2. Substitute masses in and solve for missing
mass