Chemical Reactions Notes
Chemical Reaction—a _______ in which one or more substances are converted into ___________________
Reactants—the substances that _________
Products—the new substances __________
Produces
Reactants
→ Products
Change in __________ :
●
Endergonic Reaction—energy is ____________; requires _________ ___________ to break bonds
than is given off when new bonds are formed
Endothermic Reaction—_____________________ from surroundings
Ex: Commercial cold packs usually consist of two compounds - urea and ammonium chloride in separate
containers within a plastic bag. When the bag is bent and the inside containers are broken, the two
compounds mix together and begin to react. Because the reaction is ____________________, it
___________________ from the surrounding environment and the bag gets cold.
●
Exergonic Reaction—energy is _____________; _____________________ is required to break the
original bonds than is released when new bonds form
Exothermic Reaction—______________________ or light release energy to the surroundings (usually in
the form of heat)
Ex: sodium and chlorine react so violently that flames can be seen as the ____________________ reaction
___________________________.
Chemical equation—a way to describe a chemical ____________ using chemical ______________ and
other ______________
Symbol
Meaning
→
produces, forms, yields
+
(s)
(l)
(g)
(aq)
heat
→
aqueous, a substance is
dissolved in water
The reactants are exposed
to heat
light
→
The reactants are exposed
to light
Types of Reactions
1.
Synthesis reaction—two or more substances combine to form only ____________________.
Synthesis means “to make”.
General equation (or general pattern):
A + B
→ AB
→ 2 NaCl
Ex:
2Na + Cl
Ex:
2Ag (s) +O2 (g)
Ex:
calcium + oxygen
→ calcium oxide
→ 2AgO (s)
What would you see in a ‘test tube’ if you were witness to a synthesis reaction? You would see two
different materials combine. A _________ new material appears.
2.
Decomposition reaction—___________________ breaks down into _______________________
products; “taking apart”
General equation:
AX
→A
Ex:
+ X
BaS
Ex:
→ Ba + S
2H2O (l)
Ex:
Aluminum fluoride
→ aluminum + fluoride
→ 2H2 (g) + O2 (g)
In a “test tube” you would see a single material coming ________ into more than one new material.
3.
Single Displacement Reaction—_______ element tries to __________ another element in a
compound forming a ______________________ leaving the weaker element by itself.
General equation (or pattern):
A + BC
Ex:
→ AC + B
Cu (s) + AgNO3 (aq)
→ Ag (s) + Cu(NO3)2 (aq)
4.
Double Displacement Reaction—when compounds __________ (or exchange) ions
General equation (or pattern):
XY + BC
→ XC
+ BY
→
Ex:
BaS + CaO
BaO + CaS
Ex:
zinc oxide + silver iodide
→ zinc iodide + silver oxide
Law of Conservation of Mass
Burning is an example of one the most familiar ______________ changes.
When you burn a lump of coal, atmospheric oxygen combines with the coal. The _________________ or
__________________ of ________________ differently is called a _________________________. The
chemical reaction ____________ carbon dioxide gas, water vapor, and a small amount of ash. This change
seems to involve a _______________ in the amount of ____________. A sizable piece of matter seems to
have _____________ only a ___________ amount of ash. However, careful ____________________ show
that the ________________ (grams) of the _____________ coal and oxygen _____________ the
__________________ (grams) of the carbon dioxide, water vapor and ash _________________.
Measurements of many chemical reactions lead to the
____________________________________________. This law states that matter ___________ be
_____________ nor _______________. This law applies to _____________ reactions where elements on
the _______ side of an _______________ must _____________ on the _________ side of the same
equation. Not only must the elements be the _________ on each side, but the _____________ of
_________ for each __________________ must be the __________ on each side, too.
Balanced chemical equation has the same _________ and _____ of atoms on both sides of the __________.
CHEMICAL REACTION represented by a CHEMICAL EQUATION
CaCl + F → CaF + Cl
2
2
2
2
_______________ (grams) = ______________ (grams)
Example
2KClO3 2KCl + 3O2
110g 50g + 60g
110g – 50g = 60g
5.
2H2 + O2 2H2O
4Al + 3O2 2Al2O3
150g + 10g _____g
_____g + 75g 150g
2NaCl 2Na + Cl2
N2 + 3H2 2NH3
_____g 15g + 15g
75g + _____g 200g
How many grams of sodium iodide (NaI) are produced by the following chemical reaction?
2Na + I 2NaI
2
37g + 52g _____g
6.
Dihydrogen dioxide (H O ) decomposes into dihydrogen (H O) monoxide and dioxide (O ). How much
dioxide will be produced from the grams of dihydrogen dioxide (H O ) indicated below?
2
2
2
2
3000g 2H O + � 1100g H O + ____g O
2
2
2
2
2
2
Balancing Equations Step-by-Step:
Step 1: Determine number of atoms for each element.
Mg + O2 → MgO
Mg = 1
O=2
Mg = 1
O=1
Step 2: Pick an element that is not equal on both sides of the equation.
Mg + O2 → MgO
Mg = 1
O=2
Mg = 1
O=1
Since the O atoms are not
equal, target those first.
Step 3: Add a coefficient in front of the formula with that element and adjust your counts.
Mg + O2 → 2 MgO
Mg = 1
Mg = 1 2
Adding a 2 in front of MgO will
change the number of atoms on
the product side of the equation.
Step 4: Continue adding coefficients to get the same number of atoms of each element on each side.
2 Mg + O2 → 2 MgO
Mg = 1 2
Mg = 1 2
O=2 O=12
Now we need to increase the number of Mg atoms we
have on the reactant side. Adding a 2 in front of Mg
will give us 2 atoms of Mg and balance the equation.
Practice: Is it balanced or unbalanced?
1.
__NaCl + __BeF2 → __NaF + __BeCl2
Reactants
Products
Na
Na
Cl
Cl
Be
Be
F
F
3. __CH4 + __O2 → __CO2 + __H2O
Reactants
2.
__Mg + __Mn2O3 → __MgO + __Mn
Reactants
4.
Mg
Mg
Mn
Mn
O
O
__FeCl3 + __Be3(PO4)2 → __BeCl2 + __FePO4
Reactants
Products
Products
Products
C
C
Fe
Fe
H
H
Cl
Cl
O
O
Be
Be
P
P
O
O
Conservation of Mass—the mass of the ____________ always ________ the mass of the ___________.
Matter is neither created nor ____________. Atoms are ___________________ but never lost or
destroyed.
Oxygen + Mercury
0.7 g 9.3 g
→ Mercury (II) Oxide
10.0 g
Balanced chemical equation has the same _________ and _____ of atoms on both sides of the
__________.