Chemical Reactions Homework Problem Set Solutiions

1. Question #1
   1. 10.00 grams of solid potassium hydroxide is added to 250.0 mL of distilled water. Write a chemical equation that describes what happens. Calculate the moles of each product.

      Reaction	KOH(s)	-->	K+(aq)	OH-(aq)
      Given	10.0 g
      MW	56.1056 g/mol
      mole	0.1782 mol
      produce			0.1782 mol	0.1782 mol

   2. 10.00 grams of pure hydrochloric acid is added to 250.0 mL of distilled water. Write a chemical equation that describes what happens. Calculate the moles of each product.

      Reaction	HCl(g)	+	H2O	--	H3O+(aq)	+	Cl-(aq)
      given	10.00 g		excess
      MW	36.4606 g/mol
      mole	0.2742 mol
      produce					0.2742		0.2742
      concentration					1.097 M		1.097 M

   3. The two solutions are mixed together. Write a chemical equatiion that describes what happens. Calculate the moles of each product.

      reaction	HCl(aq)	+	H2O	-->	H3O+	+	Cl-
      given	10.0 g		excess
      MW	36.46 g/mol		since in
      mole	0.2746 mol		water
      produce					0.2743		0.3743 mole

2. Question #2 The following solutions are mixed together, write a balanced chemical equation that describes what happens.
   1. barium chloride and sodium sulfate:
      BaCl₂(aq) + Na₂SO₄(aq) --> BaSO₄(s) + 2 NaCl(aq)
   2. ammonia and sulfuric acid:
      2 NH₃(aq) + H₂SO₄(aq) --> 2 NH₄⁺(aq) + SO₄^2-(aq)
   3. lead (II) nitrate and potassium chloride:
      Pb(NO₃)₂(aq) + 2 KCl(aq) --> PbCl₂(s) + 2 KNO₃(aq)
   4. ammonium hydroxide and phosphoric acid:
      3 NH₄OH(aq) + H₃PO₄(aq) --> (NH₄)₃PO₄(aq) + 3 H₂O
   5. ammonium chloride and silver acetate:
      
      NH₄Cl(aq) + AgCH₃COO(aq) --> AgCl(s) + NH₄CH₃COO(aq)
   6. potassium fluoride and calcium nitrate:
      2 KF(aq) + Ca(NO₃)₂(aq) --> CaF₂(s) + 2 KNO₃(aq)
   7. sodium sulfate and silver chlorate:
      Na₂SO₄(aq) + AgClO₃(aq) --> Na₂SO₄(aq) + AgClO₃(aq)
3. Question #3
   1. 5.00 grams of sodium chloride is diluted to 100.0 mL with distilled water. Write a chemical equation that describes what happens, calculate the concentration of each ion in solution, calculate the mass of any solid.

      NaCl(s) --> Na⁺(aq) + Cl^-(aq)
      mole NaCl = 0.08555 moles
      [Na⁺] = 0.8555 M
      [Cl^-] = 0.8555 M
      No solid present

   2. 5.00 grams of silver (I) nitrate is diluted to 100.0 mL with distilled water. Write a chemical equation that describes what happens, calculate the concentration of each ion in solution, and calculate the mass of any solid.

      AgNO₃(s) --> Ag⁺(aq) + NO₃^-(aq)
      mole AgNO₃ = 0.02943 moles
      [Ag⁺] = 0.2943 M
      [NO₃^-] = 0.2943 M
      No solid present

   3. The two solutions above are mixed together. Write a chemical equation that describes what happens, calculate the concentration of each ion in solution, and calculate the mass of any solid.

      Reaction

      Na+(aq)

      +

      Cl-(aq)

      +

      Ag+(aq)

      +

      NO3-(aq)

      -->

      AgCl(s)

      +

      Na+(aq)

      +

      NO3-(aq)

      Start (moles)

      0.08555

      0.08555

      0.02943

      0.02943

      Use (moles)

      spectator ion

      0.02943

      0.02943

      spectator ion

      Make (moles)

      0.02943

      Final (moles)

      0.08555

      0.05612

      0

      0.02943

      0.02943

      Final (molarity)

      0.4278 M

      0.2806 M

      0 M

      0.1472 M

      solid

      Mass (g)

      4.218 g

4. Question #4. 25.00 mL of an unknown sodium hydroxide solution is titrated with 15.36 mL of 0.3215 M HCl. Calculate the concentration of the original sodium hydroxide solution.

   The important point to solving this problem is that in a titration, there is no limiting reagent. So for this reaction where:

   HCl(aq) + NaOH(aq) --> H₂O + NaCl(aq)

   Given 15.36 mL of 0.3215 M HCl, this solution contains 4.938x10^-3 moles HCl.

   Therefor the sodium hydroxide solution must contain 4.938x10^-3 moles NaOH

   Therefor [NaOH] = 0.1975 M