GENERAL CHEMISTRY I
CHEM 1311.001
EXAM 2
Friday March 5, 1999


Name______________________________________________

SSN_______________________________________________

Note: For chemical equations shown in multiple choice answers, you need to look up the solubilities of the substances in the equations. You can't be sure the phase labels shown in the equations are correct, since all answers except one are intentionally incorrect.


1. When we mix solutions of two water-soluble ionic compounds, we often write a metathesis reaction to help us decide what products we might get. In writing the molecular form of the metathesis reaction, we can always swap cations and anions and get what appears to be reaction products. However, we know there is really no reaction if

a) all the ions are spectator ions

b) none of the ions are spectator ions

c) some of the ions are spectator ions and some are not

2. True or False: The spectator ions are the ions you write in the net ionic equation.
a) Trueb) False
3. What will happen (if anything) when aqueous solutions of barium bromide and sodium phosphate are mixed?

a) No precipitate will form

b) A single precipitate of barium phosphate will form

c) A single precipitate of sodium bromide will form

d) Two precipitates -- barium phosphate and sodium bromide -- will form

4. What will happen (if anything) when aqueous solutions of calcium acetate and potassium sulfate are mixed?

a) No precipitate will form

b) A single precipitate of calcium sulfate will form

c) A single precipitate of potassium acetate will form

d) Two precipitates -- calcium sulfate and potassium acetate -- will form

5. What will happen (if anything) when aqueous solutions of ammonium chloride and barium nitrate are mixed?

a) No precipitate will form

b) A single precipitate of ammonium nitrate will form

c) A single precipitate of barium chloride will form

d) Two precipitates -- ammonium nitrate and barium chloride -- will form

6. What will happen (if anything) when aqueous solutions of sodium sulfide and barium chloride are mixed?

a) No precipitate will form

b) A single precipitate of sodium chloride will form

c) A single precipitate of barium sulfide will form

d) Two precipitates -- sodium chloride and barium sulfide -- will form

7. A chemistry student was wondering what would happen if aqueous solutions of magnesium chloride and sodium hydroxide were mixed. The student wrote out the following molecular equation:

MgCl2(aq)   +   2NaOH(aq)   ----->   Mg(OH)2(s)   +   2NaCl(aq)

Which ions (if any) should be regarded as spectator ions in the reaction that occurs (if any) when these solutions are mixed?

a) Na+      b) Na+ and Cl-      c) Mg2+ and OH-

d) Na+, Mg2+, Cl-, OH-      e) There are no spectator ions in this reaction

8. Can a net ionic equation be obtained from the molecular equation in problem 7, and if so, what is it?

a) There is no net ionic equation

b) Na+(aq)   +   Cl-(aq)   ----->   NaCl(aq)

c) Mg2+(aq)   +   2OH-(aq)   ----->   Mg(OH)2(s)

d) 2Na+(aq)   +   Mg2+(aq)   +   2OH-(aq)   +   2Cl-(aq)   ----->   Mg(OH)2(s)   +   2NaCl(aq)

e) 2Na+(aq)   +   Mg2+(aq)   +   2OH-(aq)   +   2Cl-(aq)   ----->   Mg(OH)2(s)   +   2Na+(aq)   +   2Cl-(aq)

9. Which ions (if any) are spectator ions in the reaction that occurs (if any) when aqueous solutions of ammonium perchlorate and potassium carbonate are mixed?

a) NH4+ and CO32-     b) K+ and ClO4-     c) K+

d) NH4+, K+, ClO4- and CO32-     e) There are no spectator ions in this reaction

10. Referring to problem 9, the net ionic equation you could write is

a) none -- there is no net ionic equation

b) 2NH4+(aq)   +   CO32-(aq)   ----->   (NH4)2CO3(s)

c) K+(aq)   +   ClO4-(aq)   ----->   KClO4(s)

d) 2NH4+(aq)   +   2K+(aq)   +   2ClO4-(aq)   +   CO32-(aq)   ----->   (NH4)2CO3(s)   +   2KClO4(s)

e) 2NH4+(aq)   +   2ClO4-(aq)   +   K2CO3(aq)   ----->   (NH4)2CO3(s)   +   2K+(aq)   +   2ClO4-(aq)

11. Perchloric acid is a strong acid and sodium hydroxide is a strong base. The molecular form of the equation for the neutralization of perchloric acid with sodium hydroxide is

HClO4(aq)   +   NaOH(aq)   ----->   H2O(l)   +   NaClO4(aq)

Which ions are spectator ions in this reaction?

a) H+ and OH-     b) Na+ and ClO4-     c) Na+

d) H+, Na+, OH-, ClO4-     e) There are no spectator ions in this reaction

12. Nitrous acid is a weak acid and ammonia is a weak base. The molecular form of the equation for the neutralization of nitrous acid with ammonia is

HNO2(aq)   +   NH3(aq)   ----->   NH4NO2(aq)

Which ions are spectator ions in this reaction?

a) H+     b) NO2-     c) H+ and NH4+     d) H+, NH4+, NO2-

e) There are no spectator ions in this reaction

13. Hydrofluoric acid is a weak acid and sodium hydroxide is a strong base. The molecular form of the equation for the neutralization of hydrofluoric acid with sodium hydroxide is

HF(aq)   +   NaOH(aq)   ----->   H2O(l)   +   NaF(aq)

Which ions are spectator ions in this reaction?

a) H+ and OH-     b) Na+ and F-     c) Na+

d) H+, Na+, OH-, F-     e) There are no spectator ions in this reaction

14. When water appears as a product in an acid base neutralization reaction, we sometimes write it HOH instead of H2O to emphasize that the reaction is a __________reaction.
a) combinationb) combustionc) decomposition
d) displacemente) metathesis
15. The "salt" that forms as a product in an acid-base neutralization reaction gets its cation

a) from the acid in all cases

b) from the base in all cases

c) sometimes from the acid and sometimes from the base

16. The reaction

2Al(s)   +   3Pb(NO3)2(aq)   ----->   2Al(NO3)2(aq)   +   3Pb(s)

is an example of a __________reaction.
a) combinationb) combustionc) decomposition
d) displacemente) metathesis
17. The reaction

Na2SO3(s)   ----->   Na2O(s)   +   SO2(g)

is an example of a __________reaction.
a) combinationb) combustionc) decomposition
d) displacemente) metathesis
18. What is another name for a single replacement reaction?
a) combinationb) decompositionc) displacement
d) neutralizatione) metathesis
19. What is another name for a double replacement reaction?
a) combinationb) combustionc) decomposition
d) displacemente) metathesis
20. Which of the following is a combustion reaction?

a) HCl(g)   +   NH3(g)   ----->   NH4Cl(s)

b) 4NaHSO3(s)   ----->   S(s)   +   SO2(g)   +   2H2O(g)   +   2Na2SO4(s)

c) C3H8(g)   +   5O2(g)   ----->   3CO2(g)   +   4H2O(g)

d) CaCl2(aq)   +   2AgNO3(aq)   ----->   Ca(NO3)2(aq)   +   2AgCl(s)

e) Zn(s)   +   CuSO4(aq)   ----->   ZnSO4(aq)   +   Cu(s)

***   END   OF   TEST   ***


ANSWERS:

1 a      2 b      3 b      4 b      5 a     

6 c      7 b      8 c      9 d      10 a     

11 b      12 e      13 c      14 e      15 b     

16 d      17 c      18 c      19 e      20 c

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