Chemical Reactions
Writing chemical reactions
Types of chemical reactions
Reactions in aqueous solutions
(ionic equations and solubility rules)
Writing Equations
REACTANTS
PRODUCTS
“gold (III) sulfide is mixed with hydrogen gas to
produce gold and hydrogen sulfide gas”
Balancing Equations
Use coefficients to make the equation follow
the law of conservation of mass.
Copper metal reacts with an aqueous solution
of silver nitrate to produce copper (II) nitrate
and silver.
Gold (III) sulfide is mixed with hydrogen gas to
produce gold and hydrogen sulfide gas.
Hydrogen peroxide is heated to form water
vapor and oxygen gas.
Types of Reactions
There are 5 major types of reactions.
Knowing these will help you predict the
products of reactions.
There five types are: Synthesis, Decomposition,
Single Replacement, Double Replacement, and
Combustion.
Synthesis (Combination)
General form: A + B --> AB
Two reactants combine to form one product.
A and B can be elements or compounds
The product AB is always a single compound
1. Metal + oxygen --> metal oxide
2. Nonmetal + oxygen --> nonmetal oxide
3. Metal + nonmetal --> salt
4. Metal oxide + water --> base
5. Nonmental oxide + water --> acid
Decomposition
General form: AB --> A + B
A single compound breaks down into two or
more simpler products
Usually require energy or catalyst
Can be difficult to predict products
Single Replacement
General forms: A + BC --> B + AC
A + BC --> C + BA
One element replaces a second element in a
compound.
To identify, notice both the reactants and
products consist of one element and one
compound.
Produces a new element and a new compound.
Single Replacement
1. Metal + acid --> hydrogen + salt
2. Metal + water --> hydrogen + metal hydroxide
or metal oxide
3. Metal + salt --> metal + salt
(look at activity series)
4. Halogen + halogen salt --> halogen + halogen
(halogens higher will replace lower)
salt
Whether one metal will
displace another metal
from a compound depends
on the reactivities of the
two metals.
We use an activity series,
which lists metals in order
or reactivity, to make the
prediction.
A metal will replace any
metal listen below it in the
series.
Mg(s) + Zn(NO3)2(aq) -->
Mg(s) + 2AgNO3(aq) -->
Mg(s) + LiNO3(aq) -->
Double Replacement
General form: AB + CD --> AD + CB
Two compounds trade positive ions.
Usually produce a precipitate, a gas, or a
molecular compound.
For double replacement to occur, one of the
following is true:
1. one product is slightly soluble and precipitates
from solution
2. one product is a gas that bubbles out of the
mixture
3. one product is a molecular compound like water
Combustion
An element or compound reacts with oxygen,
producing energy (heat & light)
Reactants: combustion requires oxygen; usually
involves a hydrocarbon
Products: metals and carbon compounds combust.
The complete combustion of carbon produces
carbon dioxide and water
Ionic compounds do not combust; as well as
carbon molecules that already contain too much
oxygen (like carbon dioxide)
Predicting Precipitate Formation
Precipitate: an insoluble
salt; a solid
Forms in some reactions,
but not others.
Use solubility rules to
determine if a precipitate
will form.
Will a precipitate form when aqueous
solutions of Na2CO3(aq) and Ba(NO3)2(aq) are
mixed?
Stoichiometry
N2(g) + H2(g)
NH3(g)
“nitrogen gas reacts with hydrogen to produce
ammonia”
Law of Conservation of Mass: matter is not
created or destroyed; it is rearranged
Balancing chemical reactions
N2(g) + 3H2(g)
2NH3(g)
“one molecule of nitrogen gas reacts with
three molecules of hydrogen to produce two
molecules of ammonia.”
“one mole of nitrogen molecules reacts with
three moles of hydrogen molecules to form
two moles of ammonia molecules.”
Coefficients = # of moles
Mole-Mole Calculations
*** MUST HAVE A BALANCED EQUATION
FOR THIS TO WORK!
Example#6: How many moles of ammonia are
produced when 0.60 mol of N reacts with H?
N2(g) + 3H2(g)
2NH3(g)
Mass-Mass Calculations
g A --> moles A
g A --> moles of A --> moles of B --> grams of B
Example#7: Calculate the number of grams of
NH3 produced by the reaction of 5.40g of
hydrogen with an excess of nitrogen.
N2(g) + 3H2(g)
2NH3(g)