2. Word Equations
• Recall that word equations can
describe chemical reactions.
• Reactants are written to the left of
the arrow and products are written to
the right of the arrow.
• Recall how to name and write
formulas from your flowchart.
• A skeleton equation is the formulas
of the reactants and products
without the amounts included.
3. Balancing Chemical
Equations
• Skeleton equations
do not require
amounts but in order
to use actual
equations in
chemistry, a balanced
equation with
amounts must be
written.
4. Law of Conservation of
Mass
• Chemical reactions must obey
the Law of Conservation of Mass.
• Reactants must equal the
products in amount and mass.
• A balanced chemical equation
compares the amounts of
reactants to products.
5.
6.
7. An Example….
• We need two wheels to make a toy
car.
• They are sold only in twos.
• Each toy car has one car body (Cb)
and 4 wheels are necessary. (W4)
• What would be our balanced
chemical equation for the toy car?
9. Building a Tricycle….
• Again, we need one trike body (Tb)
but a tricycle has 3 wheels (W3) and
the wheels only come in packages
of two. (W2)
• How many orders of each tricycle
should be make so there are no
leftover parts?
• Write a balanced “chemical”
equation.
12. Tips and Tricks…
• If there is a polyatomic ion on
both sides of the equation,
keep it together and balance it
as one atom.
• Balance the more complicated
compounds first.
• The elements that are by
themselves should be
balanced last.
• Sometimes it is helpful to
create a chart below the
equation to keep track of the
numbers.
• If you have a word equation,
write the skeleton equation
first, then balance.
17. SUM IT UP!
• Write the
balanced
chemical
equation for the
following word
equation.
• Hydrogen + sulfur
hydrogen
sulfide
18. Types of Chemical
Reactions
• There are 5 general types of
reactions.
• Occasionally, a reaction may fit
equally into two categories.
• Identification is useful to help
determine and predict the products.
19. Combination Reactions
• It is also called a synthesis reaction.
• Two or more substances combine to
create a single new substance.
• Mg + O2 MgO
• K + Cl2 KCl
• Balance these equations!
20.
21. Decomposition Reactions
• A single compound breaks down into
two or more simpler products.
• HgO Hg + O2
• H2O H2 + O2
• Balance these equations!
22.
23. Single-Replacement Reaction
• One element replaces a second element
in a compound.
• Requires the activity series to determine
if the reaction will occur.
• The element that is higher up on the
series will replace any lower elements.
• A halogen (group 7) can replace any
other halogen providing that it is higher
up on the periodic table.
• If a reaction doesn’t occur, write NR for
no reaction.
24. Single-Replacement
Reactions
• K + H2O KOH + H2
• Zn + Cu(NO3)2 Cu + Zn(NO3)2
• Br2 + NaI NaBr + I2
• Br2 + NaCl NR
• Balance these equations!
25.
26. Double-Replacement
Reactions
• Sometimes when two solutions are
mixed, nothing happens.
• Other times, the ions in the two solutions
react.
• In these types of reactions, the two metal
(positive) cations switch places with each
other.
• Occasionally, a precipitate will form or a
gas will be generated.
• Sometimes, both products are aqueous
so you won’t see anything different
31. Combustion Reactions
• This is a chemical change that takes
place when a compound (usually a
hydrocarbon) reacts with oxygen
(O2) and produces carbon dioxide,
water and usually energy in the form
of heat and/or light.
• C8H18 + O2 CO2 + H2O
• When balancing, these numbers are
usually high.
45. Reaction in Aqueous
Solution
• Your world is water-based.
• Most reactions take place in water.
• Most equations can show the reactions between
compounds but do not show how the compounds
behave when dissolved in water.
• They actually separate into the various ions when in
aqueous solution.
• You can use these ions to write a complete ionic
equation.
• If the ion remains unchanged on both sides of the
equation, it is called a spectator ion.
• The spectator ion doesn’t participate in the reaction
directly and can be cancelled out.
• The resulting equation is called the net ionic equation.
• Remember, the resulting equation must be balanced.
46. Net Ionic Equations
• A net ionic equation shows only
those particles involved in the
reaction and is balanced with
respect to both mass and charge.
• Pb (s) + 2Ag+ (aq) 2Ag (s) + Pb +2 (aq)
• There are 2 Ag on both sides and +2
on both sides.
47. Solubility
• Soluble means it can dissolve in
water or be aqueous.
• There are rules to determine if
something is soluble or not.
• Page. 344 table 11.3 has the rules.
• If something is soluble write (aq).
• If it isn’t soluble or is insoluble, it is
solid or (s).
• Check the table for the rules.
49. Answers
• Balance this equation.
• Ca+2 + 2OH- + 2H+ + PO4-3
Ca+2 + PO4-3 + 2H2O
• First balance the charges,
then balance the numbers of
the types of atoms.
• Both sides must have an
equal charge.
50. LET’S PRACTICE!
• Write the complete
and net ionic
equations for:
• Sodium hydroxide
(aq) and
phosphoric acid
(aq) makes calcium
phosphate and
water.
• Don’t forget to use
your solubility rules.
51. Answers
• Write the complete and net ionic equations
for:
• Sodium hydroxide and phosphoric acid
makes calcium phosphate and water.
• 3Ca(OH)2 (aq) + 2H3PO4 (aq) Ca3(PO4)2 (s) +
6H2O (l)
• 3Ca +2 + 6OH- + 6H+ + 2PO4-3 3Ca+2 +
2PO4-3 + 6H2O
• 6OH- + 6H+ 6H2O
• Reduce
• OH- + H+ H2O
53. SCIENCE SWAG
• Create your own
visual
representation of
the 5 types of
chemical reactions
we have studied.
• Put them on a
poster.
• Due one week from
today.
54.
55. POST IT UP
Write a balanced net ionic equation for
Lead(II) nitrate (aq) reacting with sulfuric
acid (aq). Hint: It’s a double replacement
reaction.
I S!
TH
OT
IG
IN
EE
DH
EL
P!
