Chemistry& 141
Clark College
Homework 3
Follow the homework guidelines given in the syllabus! Show your work, use units and sig figs, where
appropriate.
1. In dilute nitric acid, copper metal dissolves according to the following balanced equation:
Cu + 4 HNO3 → Cu(NO3)2 + 2 NO2 + 2 H2O
a) How many grams of nitric acid are required to dissolve 11.45 g of Cu?
b) How many grams of NO gas are formed?
2. Nitrogen gas can be prepared by passing gaseous ammonia over solid copper (II) oxide at high
temperatures, as described by the following unbalanced equation. How many grams of N2 are
formed when 18.1 g of NH3 are reacted with 90.4 g of CuO? What starting material, if any is left
over? How many grams of that material are left over?
NH3 (g) + CuO (s) → N2 (g) + Cu (s) + H2O (g)
3. Chlorine gas reacts with sulfur dioxide to produce thionyl chloride (SOCl2), a common reagent in
organic synthesis, and dichlorine monoxide, according to the following balanced reaction:
SO2 (g) + 2 Cl2 (g) → SOCl2 (g) + Cl2O (g)
If you start with 150.0 g of each starting material, how many grams of thionyl chloride can be
produced? How much of which starting material is left over?
4. Balance the following equations, and provide the net ionic equation as well.
a) FeCl3(aq) + KOH(aq) → Fe(OH)3(s) + KCl(aq)
b) Al(s) + HNO3(aq) → Al(NO3)3(aq) + H2(g)
c) Ni(C2H3O2)2(aq) + Na2S(aq) → NiS(s) + NaC2H3O2(aq)
5. Use the solubility rules to determine if the following compounds are soluble (S) or insoluble (I). If
the compounds are soluble, break the compound up into ions.
a) Ca3(PO4)2
b) Fe(OH)3
c) Potassium carbonate
d) Lead (IV) sulfate
e) Ammonium sulfide
f) Mn(NO3)2
6. For each reaction, determine the products (assume all reactions occur in aqueous media). Give the
molecular and net ionic equations that describe the reactions. Also, classify each reaction as
precipitation, acid/base and/or redox, and separately as a single of double displacement reaction.
a) Hydrobomic acid and strontium (Sr) hydroxide.
b) Magnesium sulfate and silver nitrate.
c) Iron metal reacting with nitric acid. (form Fe+3)
d) Copper (II) sulfate reacting with sodium sulfide.
e) Barium carbonate reacting with hydrochloric acid.
f) Silver metal with phosphoric acid.
Homework 3
Fall 2008
Page 1 of 2
Chemistry& 141
Clark College
7. Looking ahead to molarity: Molarity is a way to express the amount of material (in moles) in a
volume of a given solution (in liters); it is similar to a density (mass per unit volume), but expressing
the amounts in moles rather than grams. Since it is in moles, we can use molarity as part of a
stoichiometry calculation. We will investigate using molarity in the following example:
Photographic paper is a mixture of silver salts trapped in a gelatin. Typically, that salt is silver bromide,
which is insoluble in water. During the development process, the excess (unexposed) silver bromide
must be washed off the paper. To do so, the paper is washed with a solution of sodium thiosulfate (the
“fixer”), and the following unbalanced reaction takes place:
AgBr (s) + Na2S2O3 (aq) → Na3Ag(S2O3)2 (aq) + NaBr (aq)
a) Balance the reaction.
b) Let’s say that an 8”x10” sheet of photographic paper contains 0.125 g of silver bromide. How
many moles of silver bromide is this?
c) How many moles of sodium thiosulfate are needed to react with the silver bromide?
! 0.0256 moles Na 2 S2 O3 $
& . What volume of
1L
"
%
d) The sodium thiosulfate comes as a 0.0256 M solution #
sodium thiosulfate solution (in mL) are needed to deliver the requisite moles of sodium
thiosulfate?
Homework 3
Fall 2008
Page 2 of 2