CHEMISTRY WKST
CH. 7 & 8 REVIEW (REACTIONS & EQUATIONS)
NAME: _________JMS__________________________
1) What are the 5 evidences that a chemical reaction took place?
 precipitate forms
 color change
 gas released
 temperature change

energy released
2) Consider the equation: 4Al(s) + 3O2(g) → 2Al2O3(s)
a) Name the reactants.
aluminum (Al), oxygen gas (O2)
b) Name the product.
aluminum oxide
c) Is the equation balanced?
yes
d) What is the physical state of Al2O3?
solid
e) What does the “→ “ mean?
yields
3) Change these word equations to balanced equations using symbols.
a) On heating, solid calcium carbonate yields solid calcium oxide and gaseous carbon dioxide.
CaCO3(s) → CaO(s) + CO2(g)
b) Solid lithium metal reacts with oxygen gas to form solid lithium oxide.
4Li(s) + O2(g) → 2Li2O(s)
c) Solid zinc metal reacts with aqueous hydrochloric acid to form aqueous zinc chloride and hydrogen gas.
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
4) What law requires us to balance chemical equations?
Law of Conservation of Matter
5) When balancing chemical equations, what is the only thing you are allowed to change?
The coefficients in front of the formulas of the substances in the equation.
6) Balance the following equations.
a) 3Fe + 4H2O → Fe3O4 + 4H2
b) 2AlBr3 + 3Cl2 → 2AlCl3 + 3Br2
c) 2HNO3 + Ba(OH)2 → Ba(NO3)2 + 2H2O
d) C8H16 + 12O2 → 8CO2 + 8H2O
e) Na2CO3 + 2HCl → 2NaCl + H2O + CO2
f)
3K2CO3 + 2Al(ClO4)3 → Al2(CO3)3 + 6KClO4
g) 4H2O + Cr + Na2CrO4 → 2Cr(OH)3 + 2NaOH
7) What are the 4 main driving forces in making a reaction occur?
 forming a precipitate
 forming molecular substances like water
 forming a gas
 transferring electrons (redox)
-28) What does the triangle above the arrow mean in a chemical equation?
the reactants are being heated
9) Classify each of the following statements as describing a double replacement, single replacement, combustion,
synthesis, decomposition or acid-base. There may be more than one answer for a statement—give them all.
a) O2(g) is always a reactant.
combustion
b) Reaction is always endothermic.
decomposition
c) 2 compounds reacting to form 2 products, one which is an insoluble solid, gas or water.
d) Reaction is always exothermic.
combustion, synthesis
e) Forms one product.
synthesis
f)
acid-base
Forms water and a salt.
double replacement
g) An element and a compound react to form 2 products, 1 an element and the other a compound. single repl.
h) Has only one reactant.
decomposition
10) When burning a hydrocarbon, what are the products?
CO2(g), H2O(l)
11) Classify each of the following reactions as double replacement, single replacement, combustion, synthesis,
decomposition or acid-base. Include all possibilities.
a) Cu + Cl2 → CuCl2
synthesis
b) KBr + AgNO3 → AgBr + KNO3
double replacement
c) 2Ba + O2 → 2BaO
synthesis, combustion
d) Fe + CuSO4 → FeSO4 + Cu
single replacement
e) C3H8 + 5O2 → 3CO2 + 4H2O
combustion
f)
HCl + KOH → KCl + H2O
acid-base
g) 2KClO3 → 2KCl + 3O2
decomposition
12) Tell what physical state the following would be in water.
a) K2SO4
(aq)
d) MgO
(s)
b) NH4OH (aq)
e) Cu(NO3)2
(aq)
c) BaCO3
f) AlPO4
(s)
(s)
13) List the 7 strong acids.
HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4
14) What is the main difference between strong and weak acids?
Strong acids completely dissociate (breaks up into its ions) in water whereas
weak acids only partially dissociate in water.
15) List the 7 diatomic elements and their physical state at room temperature.
H2(g), N2(g), O2(g), F2(g), Cl2(g), Br2(l), I2(s)
-316) What is the net ionic equation for all strong acids-bases reactions?
+
−
H (aq) + OH (aq) → H2O(l)
17) For each of the following molecular equations, write the ionic equation, circle the spectator ions (if any), and write the
net ionic equation.
a) Zn(NO3)2(aq) + K2CO3(aq) → ZnCO3(s) + 2KNO3(aq)
2+
−
2+
2−
+
2−
−
+
Zn (aq) + 2NO3 (aq) + 2K (aq) + CO3 (aq) → ZnCO3(s) + 2K (aq) + 2NO3 (aq)
Zn (aq) + CO3 (aq) → ZnCO3(s)
b) Mg(s) + 2AgNO3(aq) → Mg(NO3)2(aq) + 2Ag(s)
−
+
−
2+
Mg(s) + 2Ag (aq) + 2NO3 (aq) → Mg (aq) + 2NO3 (aq) + 2Ag(s)
+
2+
Mg(s) + 2Ag (aq) → Mg (aq) + 2Ag(s)
c) HClO4(aq) + LiOH(aq) → H2O(l) + LiClO4(aq)
−
+
+
−
−
+
H (aq) + ClO4 (aq) + Li (aq) + OH (aq) → H2O(l) + Li (aq) + ClO4 (aq)
−
+
H (aq) + OH (aq) → H2O(l)
18) Tell what acid and base make the following salts.
a) Ba(NO3)2
b) KClO3
acid → HNO3
base → Ba(OH)2
c) NH4Br
HClO3
KOH
HBr
NH4OH
d) Fe2(CO3)3
H2CO3
Fe(OH)3
19) When we did the single replacement lab the only reactions we did with Ca was with an acid and with H 2O. Why did
we not do the other reactions with Ca and the solutions?
Calcium reacts with H2O. Since the other solutions were in H2O, the Ca will react with the H2O as well as the
solute. In other words, the Ca + H2O reaction will interfere with the desired reactions.
20) Why does Zn react more vigorously with an acid than Sn?
Zn is much more reactive with an acid than Sn as shown by Zn being farther away from the acid on the
activity series than Sn is.
21) Why do we sometimes get a precipitate when mixing 2 solutions?
Sometimes there are 2 ions in the resulting mixture that when they come in contact with each other will form
an insoluble solid.
22) If a solution of KCl and NaCl is mixed with another solution containing MgCl 2, how many different kinds of ions are
present? Would there be a precipitate? Why or why not?
There are 4 different ions present. No there will not be a precipitate since the chlorides of the cations (the
−
positive ions) are soluble. Also, since Cl is the anion in all 3 solutions, no new substances would be formed.
23) So far this year we have seen a couple of colored solutions containing transition metals. What color is the solution
containing the following ions containing a transition metal?
2+
a) Cu
blue
2−
b) CrO4
yellow
-424) Complete and balance the following equations. Include physical states for the products.
a)
C6H6(l) + O2(g) →
CO2(g) + H2O(l)
b)
Cu(s) + AgNO3(aq) →
Cu(NO3)2(aq) + Ag(s)
c)
Pb(ClO3)2(aq) + K2SO4(aq) →
PbSO4(s) + KClO3(aq)
d)
CuO(s) →
Cu(s) + O2(g)
e)
MgCO3(s) + H2SO4(aq) →
MgSO4(aq) + CO2(g) + H2O(l)
f)
NH4OH(aq) + H3PO4(aq) →
H2O(l) + (NH4)3PO(aq)
The next one was a mistake—it doesn’t work. Change it to what is shown on the left and work it out.
g)
SO2(g) + H2O(l) →
H2SO3(aq)
h)
Na2S(aq) + Ni(NO3)2(aq) →
NaNO3(aq) + NiS(s)
i)
Ba(ClO3)2(aq) →
BaCl2(s) + O2(g)
j)
Zn(s) + CuCl2(aq) →
ZnCl2(aq) + Cu(s)
k)
AlCl3(aq) + Pb(NO3)2(aq) →
Al(NO3)3(aq) + PbCl2(s)
l)
Rb2O(s) + H2O(l) →
RbOH(aq)
m) CaO(s) + CO2(g) →
CaCO3(s)
n)
Cu(s) + Li2CO3(aq) →
NR  Cu is less reactive than Li and therefore cannot replace it.
o)
HgO(l) →
Hg(l) + O2(g)
p)
K(s) + Cl2(g) →
KCl(s)
q)
Cl2(g) + KBr(aq) →
KCl(aq) + Br2(l)
r)
H2SO3(g) →
H2O(l) + SO2(g)
s)
BaCO3(s) →
BaO(s) + CO2(g)
t)
K(s) + H2O(l) →
KOH(aq) + H2(g)
u)
BaCl2(s) + O2(g) →
Ba(ClO3)2(s)
v)
RbOH(s) →
Rb2O(aq) + H2O(l)
VOCAB TO KNOW:
electrolyte: Substance that conducts electricity when dissolved or melted
endothermic: process that absorbs energy (heat)
exothermic: process that gives off energy (heat)
hydrocarbon: compound made up of carbon and hydrogen
insoluble: won’t dissolve
oxidation: process that loses electrons
precipitate: solid formed by the reaction between two solutions
products: substances formed in a reaction—they will be on the right side of the arrow in a chemical equation
reactants: substances that begin a reaction—they will be on the left side of the arrow in a chemical equation
reduction: process that gain electrons
soluble: will dissolve