NAMING FORMULAS
Transcript of NAMING FORMULAS
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CHEMICAL EQUATIONS AND MOLES
Unit 5
NAMING
FORMULAS
NOMENCLATURE: NAMING COMPOUNDS
Determine if the compound is:
1. Ionic
2. Covalent
3. Acid
NAMING COMPOUNDS
Types of Compounds
Ionic
Metal and a negative ion
(polyatomic ions)
Covalent Binary Compound of 2
nonmetals
Acids
H___(aq)
Like ionic where H acts like the metal
IDENTIFYING COMPOUNDS
Ionic Compounds
have ionic bonds
contain a metal and a nonmetal
may contain polyatomic ions Table E
Covalent Compounds
have covalent bonds
between 2 or more nonmetals
NO ions
Acids
Start with an H
Table K
THINK ABOUT SOME OF THE NAMES YOU ALREADY KNOW:
Sodium chloride, NaCl
Carbon dioxide, CO2
Sulfuric acid, H2SO4
Carbon monoxide, CO
Copper II sulfate, CuSO4
Carbonic acid, H2CO3
Calcium carbonate, CaCO3
Hydrochloric acid, HCl
Diphosphorous pentoxide, P2O5
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IDENTIFY THE FOLLOWING AS AN IONIC
COMPOUND, COVALENT COMPOUND OR AN ACID:
HNO3
K2SO4
Li2O
NO
Mg(SCN)2
NH4OH
NaHCO3
SO2
CH3COOH
Ca(OH)2
H3PO4
NaOH
PbSO3
PbSO4
H2SO4
Pb(SO4)2
COMMON NAMES
A lot of chemicals have common names as well
as the proper IUPAC name.
Chemicals that should always be named by
common name and never named by the IUPAC
method are:
H2O water, not dihydrogen monoxide
NH3 ammonia, not nitrogen trihydride
CATION +
ANION --->
COMPOUND
A neutral compound
requires
equal number of +
and - charges.
COMPOUNDS FORMED FROM IONS
Na+ + Cl- --> NaCl
Predicting Charges on Monatomic Ions KNOW THESE !!!!
+1 +2 -3 -2 -1 0
Cd+2
IONIC COMPOUNDS
NH4+
Cl-
ammonium chloride, NH4Cl
NO3-
nitrate ion
NO2-
nitrite ion
POLYATOMIC IONS
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NAMING MOLECULAR COMPOUNDS
CH4 methane BCl3
boron trichloride
CO2 Carbon dioxide
All are formed
from two or
more
nonmetals.
Ionic
compounds
generally
involve a metal
and nonmetal
(NaCl)
MOLECULAR (COVALENT) NOMENCLATURE
FOR TWO NONMETALS
Prefix System (binary compounds)
1. Less electronegative atom comes first.
2. Add prefixes to indicate # of atoms. Omit mono- prefix on the FIRST element. Mono- is OPTIONAL on the SECOND element (in this class, it’s NOT optional!).
3. Change the ending of the second element to -ide.
PREFIX
mono-
di-
tri-
tetra-
penta-
hexa-
hepta-
octa-
nona-
deca-
NUMBER
1
2
3
4
5
6
7
8
9
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MOLECULAR NOMENCLATURE PREFIXES
• CCl4
• N2O
• SF6
• carbon tetrachloride
• dinitrogen monoxide
• sulfur hexafluoride
MOLECULAR NOMENCLATURE:
EXAMPLES MIXED PRACTICE
1. Dinitrogen monoxide
2. Potassium sulfide
3. Copper (II) nitrate
4. Dichlorine heptoxide
5. Chromium (III) sulfate
6. Iron (III) sulfite
7. Calcium oxide
8. Barium carbonate
9. Iodine monochloride
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MIXED PRACTICE
1. BaI2
2. P4S3
3. Ca(OH)2
4. FeCO3
5. Na2Cr2O7
6. I2O5
7. Cu(ClO4)2
8. CS2
9. B2Cl4
ACID NOMENCLATURE
Acids
Compounds that form H+ in water.
Formulas usually begin with ‘H’.
In order to be an acid instead of a gas, binary acids must be
aqueous (dissolved in water)
Ternary acids are ALL aqueous
Examples:
HCl (aq) – hydrochloric acid
HNO3 – nitric acid
H2SO4 – sulfuric acid
NAME THE FOLLOWING ACIDS
HI (aq)
HCl
H2SO3
HNO3
WRITE THE FORMULA!
Hydrobromic acid
Nitrous acid
Carbonic acid
Phosphoric acid
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CHEMICAL
EQUATIONS
OBJECTIVES
Recognize evidence of chemical change.
Represent chemical reactions with equations.
Classify chemical reactions.
Describe aqueous solutions.
Write complete ionic equations for chemical
reactions in aqueous solutions.
Predict whether reactions in aqueous solutions
will produce a precipitate, water, or a gas.
KEY WORDS CHEMICAL EQUATIONS
A chemical equation is written as an
expression similar to a mathematic
equation that can be compared to a
recipe that a chemist follows in order to
produce desired results.
CHEMICAL EQUATIONS
All chemical equations have reactants and products.
We express a chemical equation as follows:
Reactants Products
The arrow is equivalent to an “=“ math. When we describe the equation we use the word “yields” or “produces” instead of equals
ANATOMY OF A CHEMICAL EQUATION
Products appear on the right
side of the equation.
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
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ANATOMY OF A CHEMICAL EQUATION
The states of the reactants and products are written in parentheses to the right of each compound.
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
ANATOMY OF A CHEMICAL EQUATION
Coefficients are inserted to
balance the equation.
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
SUBSCRIPTS AND COEFFICIENTS GIVE DIFFERENT
INFORMATION
Subscripts tell the number of atoms of
each element in a molecule
THE STATE OF MATTER SYMBOLS
These 4 symbols represent the state in which
the element or compound is currently in.
1. Solid: (s)
2. Liquid: (l)
3. Gas: (g)
4. Aqueous: (aq): dissolved in water. Ex. Salt in
Water.
EQUATION TYPES
Two Types of Chemical Equations:
1. Word Equations: use words to describe the
elements or compounds present.
Iron (s) + Chlorine (g) Iron (III) Chloride (s)
2. Skeleton Equations: use symbols for the
elements or compounds present.
Much less cumbersome.
Fe (s) + Cl2 (g) FeCl3 (s)
EVIDENCE OF CHEMICAL REACTIONS
First, we need a definition: Chemical Reaction:
the process by which the atoms of one or more
substances are rearranged to form different
substances.
What evidence suggests to you that a chemical
reaction has taken place?
Color change, fizz, burst, burn, temperature
change, odor, sudden appearance of a solid in a
liquid.
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REACTION
TYPES
IDENTIFYING REACTION TYPES
Reactions are classified by their products.
5 basic types of chemical reactions are:
synthesis or combination reactions
decomposition reactions
single replacement reactions
double replacement reactions
combustion reactions
SYNTHESIS (COMBINATION) REACTIONS
Examples:
N2 (g) + 3 H2 (g) 2 NH3 (g)
C3H6 (g) + Br2 (l) C3H6Br2 (l)
2 Mg (s) + O2 (g) 2 MgO (s)
Two or more
substances
react to form
one product
DECOMPOSITION REACTIONS
Examples:
CaCO3 (s) CaO (s) + CO2 (g)
2 KClO3 (s) 2 KCl (s) + O2 (g)
2 NaN3 (s) 2 Na (s) + 3 N2 (g)
One substance breaks
down into two or more
substances
SINGLE REPLACEMENT REACTIONS
Single replacement reactions occur when one
chemical takes the place of another in a
reaction.
In the typical single replacement reaction, an
element trades places with one of the ions in a
compound.
SINGLE REPLACEMENT REACTIONS
A + CD AD + C
Note: Element A replaces ion C in the reaction.
The clue in this reaction is:
Element+Compound Element + Compound
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TYPE: SINGLE DISPLACEMENT
Example: Zn + CuCl2
Zn Cl Cl Cu +
General: AB + C AC + B
Cl Cl Zn Cu +
See Reference Tables
THE ACTIVITY SERIES
THE ACTIVITY SERIES
We have looked at several reactions: Fe + CuSO4 Cu + Fe2(SO4)3 Li + H2O LiOH + H2 Such experiments reveal trends. The activity series ranks the relative reactivity of metals. It allows us to predict if certain chemicals will undergo single displacement reactions when mixed: metals near the top are most reactive and will displacing metals near the bottom.
Fe + CuSO4
Ni + NaCl
Li + ZnCO3
Al + CuCl2
Cu + Fe2(SO4)3
NR (no reaction)
Zn + Li2CO3
Cu + AlCl3
Q: Which of these will react?
H is the only nonmetal listed. H2 may be displaced from acids or can be given off when a metal reacts with H2O (producing H2 + metal hydroxide). The reaction with H2O depends on metal reactivity & water temp.
A: No for cold, yes if it is hot/steam
Mg + H2O
H2 + ZnCl2
H2 + Mg(OH)2
Q: Zn + HCl
Q: will Mg react with H2O?
DOUBLE REPLACEMENT REACTIONS
Double replacement reactions are
identified by two ions trading places and
forming new compounds.
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DOUBLE REPLACEMENT REACTIONS
AB + CD AD + CB
Note: Notice that one ion from compound AB
replaces one ion from compound CD.
Clue:
Compound+CompoundCompound+Compound
DOUBLE REPLACEMENT REACTIONS OCCUR
ONLY IF:
water is a product
A gas is produced (HCl)
A precipitate is produced
You must predict the product or there is no
reaction!
TYPE: DOUBLE REPLACEMENT
Example: MgO + CaS
General: AB + CD AD + CB
S O
Mg Ca +
O S
Mg Ca +
COMBUSTION REACTIONS
Examples:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g)
Rapid reactions that
produce a flame
Most often involve
hydrocarbons
reacting with oxygen
in the air
COMBUSTION REACTIONS
Combustion reactions are the ones that burn (or explode!). There are two types of combustion reactions—complete or incomplete reactions.
These reactions are identified by their products. They either produce carbon monoxide and water or carbon dioxide and water.
COMPLETE COMBUSTION REACTIONS
These reactions burn “efficiently” which
means they produce carbon dioxide and
water. These reactions typically burn
cleanly and leave very little residue
behind.
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COMPLETE COMBUSTION REACTIONS
CH4 + O2 CO2 + H2O
They may also be written:
CH4 CO2 + H2O
(O2 is usually written above the arrow.)
Clue: CO2 (carbon dioxide) in the product
along with water
CONSERVATION OF MATTER
The law of conservation of matter tells
us that matter can neither be created
nor destroyed. It is transformed from
one form to another.
We follow the conservation of matter law
when we balance equations.
BALANCING A CHEMICAL EQUATION
A chemical equation is balanced when the
ions or atoms found on the reactant side
of the equation equals that found on the
product side.
The arrow can be considered the balance
point.
COEFFICIENTS
We use coefficients in front of elements or
compounds on either side of the
reaction to balance the equation. (The
coefficients go in front of the chemical!)
We cannot change subscripts because it
would create new materials that are not
part of reaction process.
The equation is balanced only by adjusting the coefficients of the
formulas as necessary to get whole number coefficients.
NEVER introduce extraneous formulas
NEVER change subscripts of the formulas
Balancing Equations
Why?-----Atoms are conserved in chemical reactions
A chemical equation is made up of reactants on the left
And the products on the right. An arrow signifies reactants
going to products
BALANCING EQUATIONS: MGO
The law of conservation of mass states that
matter can neither be created or destroyed
Thus, the number of a particular atom is the
same on both sides of a chemical equation
Example: Magnesium + Oxygen
Mg + O2 MgO
However, this is not balanced
O Mg O + Mg O
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BALANCE EQUATIONS BY “INSPECTION”
From Mg + O2 MgO
2Mg + O2 2MgO is correct
Mg + ½O2 MgO is incorrect
Mg2 + O2 2MgO is incorrect
4Mg + 2 O2 4MgO is incorrect
BALANCE THIS EQUATION!
Na + Cl2 NaCl
Na- 1 Na-1
Cl- 2 Cl-1
**note that the number of sodiums balance but the chlorine does not. We will have to use coefficients in order to balance this equation.
INSERTING SUBSCRIPTS
Na + Cl2 2 NaCl
Na- 1 Na-1 2
Cl- 2 Cl-1 2
** Now the chlorine balances but the
sodium does not! So we go back and
balance the sodium.
FINALLY BALANCED!
2Na + Cl2 2 NaCl
Na- 1 2 Na-1 2
Cl- 2 Cl-1 2
**Since the number of each element on the reactant side and the product side of the equation are equal, the equation is balanced.
BALANCING EQUATION PRACTICE
Hints: start with elements that occur in
one compound on each side. Treat
polyatomic ions that repeat as if they
were a single entity.
Balancing Chemical Equations
1. Write the correct formula(s) for the reactants on
the left side and the correct formula(s) for the
product(s) on the right side of the equation.
Ethane reacts with oxygen to form carbon dioxide and water
C2H6 + O2 CO2 + H2O
2. Change the numbers in front of the formulas
(coefficients) to make the number of atoms of
each element the same on both sides of the
equation. Do not change the subscripts.
3.7
2C2H6 NOT C4H12
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BALANCING EQUATION PRACTICE
a) P4 + O2 P4O10
b) Li + H2O H2 + LiOH
c) Bi(NO3)3 + K2S Bi2S3 + KNO3
d) C2H6 + O2 CO2 + H2O
C2H6 + O2 CO2 + H2O
FORMULA
WEIGHTS
FORMULA WEIGHT (FW)
Sum of the atomic weights for the atoms in a chemical formula
So, the formula weight of calcium chloride, CaCl2, would be
Ca: 1(40.1 amu)
+ Cl: 2(35.5 amu)
111.1 amu
These are generally reported for ionic compounds
MOLECULAR WEIGHT (MW)
Sum of the atomic weights of the atoms in
a molecule
For the molecule ethane, C2H6, the
molecular weight would be
C: 2(12.0 amu) + H: 6(1.0 amu)
30.0 amu
PERCENT COMPOSITION
One can find the percentage of the mass of
a compound that comes from each of the
elements in the compound by using this
equation:
% element = (number of atoms)(atomic weight)
(FW of the compound) x 100
PERCENT COMPOSITION
So the percentage of carbon in ethane is…
%C = (2)(12.0 amu)
(30.0 amu)
24.0 amu
30.0 amu = x 100
= 80.0%
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MOLES
MOLES
74
Moles Mass of
Element
Mass of
Compound
Atoms of
Element
Molecules of
Compound
Volume of
gas (STP)
/ atomic mass =
= atomic mass x
= 6.02 x 1023 /
X 6.02 x 1023 =
/ 22.4
L =
= 2
2.4
L x
AVOGADRO’S NUMBER
6.02 x 1023
1 mole of 12C has a
mass of 12 g
MOLAR MASS
By definition, these are the mass of 1 mol of a
substance (i.e., g/mol)
The molar mass of an element is the mass number
for the element that we find on the periodic table
The formula weight (in amu’s) will be the same
number as the molar mass (in g/mol)
1 mole of a gas occupies 22.4 liters in volume.
USING MOLES
Moles provide a bridge from the molecular scale to
the real-world scale
MOLE RELATIONSHIPS
One mole of atoms, ions, or molecules contains
Avogadro’s number of those particles
One mole of molecules or formula units contains
Avogadro’s number times the number of atoms or
ions of each element in the compound
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FINDING
EMPIRICAL
FORMULAS
IDENTIFYING EMPIRICAL FORMULAS
Empirical formulas are the reduced formula.
Ex. Molecular formula C6H12
Empirical formula is CH2
ELEMENTAL ANALYSES
Compounds
containing other
elements are
analyzed using
methods analogous
to those used for C, H
and O
STOICHIOMETRIC CALCULATIONS
The coefficients in the balanced equation give the
ratio of moles of reactants and products
STOICHIOMETRIC CALCULATIONS
From the mass of
Substance A you can
use the ratio of the
coefficients of A and B
to calculate the mass
of Substance B formed
(if it’s a product) or
used (if it’s a reactant)