Download Chemical Reactions

Chemical Reactions
Unit 5
Word Equations
• To write a word equation, write the names of the
_________________ to the left of the arrow
separated by plus signs; write the names of the
______________ to the right of the arrow, also
separated by plus signs.
• Examples: Reactant + Reactant  Product + Product
methane + oxygen  carbon dioxide + Water
iron + oxygen  iron(III) oxide
hydrogen peroxide  water and oxygen
Rules for Writing and Balancing Equations
1. Determine the correct formulas for all 4. Balance the elements one at a time by
the reactants and products.
using coefficients. When no coefficient
is written, it is assumed to be 1. Begin by
2. Write the skeleton equation by placing
the formulas for the reactants on the left balancing elements that appear only
and the formulas for the products on the once on each side of the equation.
Never balance an equation by changing
right with a yields sign (→) in between.
If two or more reactants or products are the subscripts in a chemical formula.
Each substance has only one correct
involved, separate their formulas with
formula.
plus signs.
3. Determine the number of atoms of each 5. Check each atom or polyatomic ion to be
sure they are equal on both sides of the
element in the reactants and products.
Count a polyatomic ion as a single unit if equation.
it appears unchanged on both sides of the 6. Make sure all the coefficients are in the
equation.
lowest possible ratio.
Chemical Equations
• A chemical equation is a representation of a
chemical ________________; the formulas of the
reactants (on the left) are connected by an arrow
(yield) with the formulas of the products (on the
right).
• A ________________ equation is a chemical
equation that does not indicate the relative
_______________ of the reactants and products.
• Here is the equation for the reaction that
produces rust:
• Fe + O2  Fe2O3
Writing Chemical Equations
• A ______________ is a substance that speeds up the
reaction but is ________ used up in the reaction.
Without Catalyst
With Catalyst
Example of Chemical Equations
• This is a balanced equation for making a bicycle.
The numbers are called coefficients—small whole
numbers that are placed in front of the formulas in
an equation in order to balance it.
Describing Chemical Reactions
• A chemical reaction is also described by a
_______________ equation in which each side of
the equation has the same number of atoms of each
element and mass is _________________.
Reaction Types
• The __________ general types of
reaction are combination,
decomposition, _________replacement, ___________-replacement
and combustion.
• The number of elements and/or
compounds reacting is a good indicator
of possible reaction type and thus
possible products.
Combination Reactions
• A combination or _______________ reaction is a
chemical change in which two or more substances
react to form a _______________ new substance.
Decomposition Reactions
• A decomposition reaction is a chemical change in
which a _____________ compound breaks down
into _______ or more simpler products.
Single-Replacement Reactions
• A single-replacement reaction is a chemical change
in which _______ element replaces a second
element in a __________________.
Double-Replacement Reactions
• A double-replacement reaction is a chemical change
involving an exchange of _________________ ions
between two compounds.
• Double-replacement reactions always involve two
ionic compounds.
Combustion Reactions
• A combustion reaction is a chemical change in which an
element or a compound reacts with __________________,
often producing energy in the form of heat and light.
Activity Series
• The activity
series of metals
lists metals and
___________ in
order of
decreasing
reactivity.
General Reaction Equations
General Reaction Equations
General Reaction Equations
Remember that there are two possible types of combustion reactions.
•Complete combustion reactions yield carbon dioxide and water.
•Incomplete combustion reactions yield carbon monoxide and water.
Ionic Equations
• A _______ ionic equation shows only those particles
involved in the reaction and is balanced with respect
to both __________ and ____________.
• You can predict the formation of a ______________
by using the general rules for solubility of ionic
compounds.
Complete Ionic Equations
• A complete ionic equation is an equation that shows
dissolved ionic compounds as _________________
free ions.
Net Ionic Equations
• An ______ that appears on both sides of an
equation and is not directly involved (is
______________) in the reaction is called a
_______________ ion.
• The net ionic equation is an equation for a reaction
in solution that shows only those particles that are
directly involved in the chemical change.
Net Ionic Equations
• Example: Sodium ions and nitrate ions are _______
changed during the chemical reaction of silver nitrate
and sodium chloride so the net ionic equation is
Predicting the Formation of a Precipitate
• You can predict the
formation of a
precipitate by using
the general rules for
_______________ of
ionic compounds.
Precipitate Example
• Will a precipitate form when a sodium carbonate
solution is mixed with a barium nitrate solution?
Sodium nitrate is _____________ but barium carbonate
is insoluble. Therefore we would write the net ionic
equation as follows.
Chemical Changes
• A chemical change is also called a chemical
______________.
• One or more substances change into one or more
new substances during a chemical reaction.
• A substance present at the ____________ of the
reaction is a _________________.
• A substance produced in the reaction is a
______________.
Chemical Changes
• Possible clues to chemical change
include:
• a transfer of _____________
• a ____________ in color
• the production of a _______
• the formation of a precipitate
• A precipitate is a __________ that forms
and settles out of a ______________
mixture.
Conservation of Mass
• During any chemical reaction, the mass of the
products is ____________ equal to the mass of the
reactants.
• The law of conservation of mass states that in any
physical change or chemical reaction,
____________ is conserved.