Chemistry - 3 rd Quarter Assessment
1. When wood burns, a small amount of ashes is made. Why is the mass of the wood before
the fire not equal to the mass of the ashes after the reaction?
a. The mass of the wood has been destroyed.
b. The mass of wood and oxygen that allowed it to burn equals the mass of the ashes
and the gas given off.
c. The mass of the wood and ashes equals the mass of the oxygen and smoke given off
during burning
d. The wood has holes in it so it is actually lighter in mass than it appears. The mass of
just the wood will equal the mass of just the ashes after burning.
2.
Which of the following best illustrates the Law of Conservation of Mass? a. H
2
O
2
 H
2
O + O b.
Na + CuS  Na
2
2
S + Cu c.
K + AgCl  KCl + Ag d.
NaOH + 2 HCl  NaCl + H
2
O
Use the following chemical reaction to answer questions 3-7.
2C
2
H
6
+ 7O
2
 4 CO
2
+ 6 H
2
O + E
3.
In the reaction oxygen is a a.
coefficient b.
reactant c.
product d.
mole
4.
In the reaction water is a a.
coefficient b.
reactant c.
product d.
mole
5.
How many moles of carbon dioxide are in the reaction? a.
2 b.
7 c.
4 d.
6
6.
What type of reaction does the equation represent? a.
synthesis b.
decomposition c.
single replacement d.
combustion

7.
The mole to mole ratio of the products is a.
2:3 b.
1:3 c.
3:2 d.
2:7
8.
CaCO
3
 CaO + CO
2
is an example of what type of reaction? a.
synthesis b.
decomposition c.
combustion d.
replacement
9.
3BaI
2
+ Sr
3
(PO
4
)
2
 Ba
3
(PO
4
)
2
+3SrI
2
is an example of what type of reaction? a.
synthesis b.
decomposition c.
single replacement d.
double replacement
10.
What stoichiometric coefficients are needed to balance the following equation:
____Al
2
S
3
+ _____KBr  ____AlBr
3
+ _____K
2
S a.
1,3,2,3 b.
1,6,2,3 c.
2,3,1,6 d.
2,12,4,6
Use the activity series below to answer questions 11-12

11.
Predict what products are formed when ZnCl and Ca react. a.
ZnCa and Cl
2 b.
CaCl
2
and Zn c.
CaZn and Cl
2 d.
no reaction occurs
12.
Predict what products are formed when MgSO
4
and Ag react. a.
AgSO
4
and Mg b.
MgAg and SO
4 c.
MgS and Ag
2
O d.
no reaction occurs
13.
A mole is equal to a.
6.02 x 10 -23 particles b.
6.02 x 10 23 particles c.
6.02 x 1023 grams d.
6.02 x 10 23 grams
14.
How many atoms are there in 3.0 moles of carbon? a.
3 b.
6.02 x 10 23 c.
1.806 x 10 23 d.
1.806 x 10 24
15.
How many moles of phosphorus are there in 15.0 g? a.
464.55 moles b.
2.06 moles c.
.484 moles d.
15.0 moles
16.
Predict the products and balance the equation for the double replacement reaction in which potassium sulfide and aluminum oxide react.
Balanced equation _________________________________________________________________
17.
If 5.00 grams of potassium sulfide react with an excess of aluminum oxide, how many grams of aluminum sulfide are formed? Show your work.

18.
If you want to form 50.0 grams of aluminum sulfide how many grams of aluminum oxide will you need to start with (potassium sulfide is in excess).
Show your work.
19.
If you react 10.0 grams of potassium sulfide with 15.0 grams of aluminum oxide, what will be the limiting reactant? Which is the excess reactant? Show your work.
20.
How much aluminum sulfide is formed in problem #19? Show your work

Answer Key
1.
b
2.
c
3.
b
4.
c
5.
c
6.
d
7.
a
8.
b
9.
d
10.
b
11.
b
12.
d
13.
b
14.
d
15.
c
16.
3K
2
S + Al
2
O
3
 2Al
2
S
3
+ 3K
17.
2.7 g Al
2
S
3
18.
33.9 g Al
2
O
3
19.
K
2
S is the limiting reactant : 3.08 g Al
2
O
3
is needed to react with 10.0 g of K
2
S or 48.7 g of K
2
S is needed to react with 15 g Al
2
O
3
20.
4.54 g Al
2
S
3