Chemistry - 3rd 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. H2O2 ® H2O + O2

b.  Na + CuS ® Na2S + Cu

c.  K + AgCl ® KCl + Ag

d.  NaOH + 2 HCl ® NaCl + H2O

Use the following chemical reaction to answer questions 3-7.

2C2H6 + 7O2 ® 4 CO2 + 6 H2O + 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.  CaCO3 ® CaO + CO2 is an example of what type of reaction?

  1. synthesis
  2. decomposition
  3. combustion
  4. replacement

9.  3BaI2 + Sr3(PO4)2 ® Ba3(PO4)2 +3SrI2 is an example of what type of reaction?

  1. synthesis
  2. decomposition
  3. single replacement
  4. double replacement

10.  What stoichiometric coefficients are needed to balance the following equation:

____Al2S3 + _____KBr ® ____AlBr3 + _____K2S

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.

  1. ZnCa and Cl2
  2. CaCl2 and Zn
  3. CaZn and Cl2
  4. no reaction occurs

12.  Predict what products are formed when MgSO4 and Ag react.

  1. AgSO4 and Mg
  2. MgAg and SO4
  3. MgS and Ag2O
  4. no reaction occurs

13.  A mole is equal to

  1. 6.02 x 10-23 particles
  2. 6.02 x 10 23 particles
  3. 6.02 x 10-23 grams
  4. 6.02 x 1023 grams

14.  How many atoms are there in 3.0 moles of carbon?

  1. 3
  2. 6.02 x 1023
  3. 1.806 x 1023
  4. 1.806 x 1024

15.  How many moles of phosphorus are there in 15.0 g?

  1. 464.55 moles
  2. 2.06 moles
  3. .484 moles
  4. 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.  3K2S + Al2O3 ® 2Al2S3 + 3K

17.  2.7 g Al2S3

18.  33.9 g Al2O3

19.  K2S is the limiting reactant : 3.08 g Al2O3 is needed to react with 10.0 g of K2S or 48.7 g of K2S is needed to react with 15 g Al2O3

20.  4.54 g Al2S3