Answers to Review Problems for Chemistry 2nd Semester Exam

Unit 6: States of Matter

1.  (a) 2H₂O₂(aq)  --> 2H₂O(l)  +  O₂(g)
     (b) 6.62 g H₂O
     (c) 4.12 L O₂
     (d) V = 4.71 L

2.  Work out your own review notes based on the chapter reading and class notes.

Unit 7: Solutions

1.  (a)  saturated solution: a solution that contains the maximum amount of solute that it can hold at that temperature.  This solution would be at its solubility.
            unsaturated solution:  This is a solution that contains less solute dissolved than its solubility.
            supersaturated solution: This is an unstable solution that contains more solute dissolved than is possible at the given temperature conditions.

        (b) Molarity = moles solute/vol of solution in Liters

        (c)  Freezing point Depression, Boiling Point Elevation, Vapor Pressure Reduction, Osmotic Pressure

2.  35 g NaOH
3.  0.141 M Na⁺
4.  3Mg(OH)₂(aq) + 2(NH₄)₃PO₄(aq) --> Mg₃(PO₄)₂(s) + 6NH₃(g) + 6H₂O(l)
    3Mg²⁺(aq) + 6OH^-(aq) + 6NH₄⁺(aq) + 2PO₄^- (aq) --> Mg₃(PO₄)₂(s) + 6NH₃(g) + 6H₂O(l)  (total ionic)
       3Mg²⁺(aq) + 6OH^-(aq) + 6NH₄⁺(aq) + 2PO₄^- (aq) --> Mg₃(PO₄)₂(s) + 6NH₃(g) + 6H₂O(l)  (net ionic)

Unit 8: Acid/Bases

1.  Strong Acids: HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄
    Strong Bases: NaOH, Ca(OH)₂, KOH, CaO

2.  low pH:  H₃PO₄, HC₃H₅O₂,  HOCl, NaCl, KF, CH₃NH₂, NaOH,  Mg(OH)₂  high pH

3.  (a) pH = 1.70, pOH = 12.30, [OH^-] = 5 x 10^-13 M
     (b) pH = 10.72, pOH = 3.28, [OH^-] = 5.2 x 10^-4 M

4.  B-L Acid: substance that is a proton donor.  B-L base: substance that is a proton acceptor.  Arrhenius Acid: substance that produces H₃O⁺ in solution.  Arrhenius Base: substance that produces OH^- in solution.

5.   [OH^-] = 7.0 x 10^-3 M, pH = 11.85, pOH = 2.15, [H₃O⁺] = 1.4 x 10^-12 M

6.  (a) The base is added to the acid since the pH starts low and then increases as the titration takes place.
     (b) At about 23 mL the equivalence point was reached.
     (c) pH of salt = 8
     (d) Weak acid and strong base