Download Chapter 7: Challenge Review Worksheet

Chapter 7: Challenge Review Worksheet
1. The coefficients represent the relative numbers of molecules involved in the
reaction. They
also can represent the relative numbers of moles of molecules (in fact, this is the
most
convenient way of thinking about coefficients). Since we can have fractions of
moles, the
coefficients can be fractions. Subscripts represent numbers of each type of atom
in a
molecule. Since we cannot have fractions of atoms, the subscripts cannot be
fractions.
2. The balance equations are given as follows:
a. 3NaBH4 + 4BF3 3NaBF4 + 2B2H6 sum of coefficients = 12
b. 2NO + 2H2 N2 + 2H2O sum of coefficients = 7
c. Fe2O3 + 3CO 2Fe + 3CO2 sum of coefficients = 9
3. a. 2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)
2K(s) + 2H2O(l) 2KOH(aq) + H2(g)
b. 2Na(s) + Cl2(g) 2NaCl(s)
2K(s) + Cl2(g) 2KCl(s)
c. 3Na(s) + P(s) Na3P(s)
3K(s) + P(s) K3P(s)
d. 6Na(s) + N2(g) 2Na3N(s)
6K(s) + N2(g) 2K3N(s)
e. 2Na(s) + H2(g) 2NaH(s)
2K(s) + H2(g) 2KH(s)
4. CO2(g) + H2O(l) + NH3(aq) + NaCl(aq) NaHCO3(s) + NH4Cl(aq)
5. C12H22O11(s) + 12O2(g) 12CO2(g) + 11H2O(g) (Water might be listed as a
liquid.)
6. Pb(NO3)2(aq) + 2NaCl(aq) PbCl2(s) + 2NaNO3(aq)
7. a. 4Fe(s) + 3O2(g) 2Fe2O3(s)
b. 4Al(s) + 3O2(g) 2Al2O3(s)
Answer Key
Chapter 8: Challenge Review Worksheet
1. Just because we leave the spectator ions out when writing a net ionic equation
for a
reaction does not mean that the spectator ions do not have to be present. The
spectator ions
are needed to provide a balance of charge in the reactant compounds for the
ions that
combine to form the precipitate. For a reaction in which silver chloride is formed,
it would
not be possible to have a reagent bottle containing just silver ions (there would
have to be
some negative ions present) or just chloride ions (there would have to be some
positive
ions present).
2. Yes, strong acids and bases are also strong electrolytes. The common strong
acids are HCl
(hydrochloric), HNO3 (nitric), H2SO4 (sulfuric), and HClO4 (perchloric). The most
common
strong bases are the alkali metal hydroxides, particularly NaOH (sodium
hydroxide) and
KOH (potassium hydroxide).
3. HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)
HNO3(aq) + NaOH(aq) NaNO3(aq) + H2O(l)
H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + H2O(l)
HCl(aq) + KOH(aq) KCl(aq) + H2O(l)
HNO3(aq) + KOH(aq) KNO3(aq) + H2O(l)
H2SO4(aq) + 2KOH(aq) K2SO4(aq) + 2H2O(l)
4. a. Ba(NO3)2(aq) + K2CrO4(aq) BaCrO4(s) + 2KNO3(aq)
b. NaOH(aq) + HC2H3O2(aq) H2O(l) + NaC2H3O2(aq)
(then evaporate the water from the solution)
c. AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
d. Pb(NO3)2(aq) + H2SO4(aq) PbSO4(s) + 2HNO3(aq)
e. 2NaOH(aq) + H2SO4(aq) Na2SO4(aq) + 2H2O(l)
(then evaporate the water from the solution)
f. Ba(NO3)2(aq) + Na2CO3(aq) BaCO3(s) + 2NaNO3(aq)
5. No. Since an oxidation–reduction process represents the transfer of electrons
between
species, you can’t have one without the other also taking place. The electrons
lost by one
species must be gained my some other species.
Answer Key
6. The different ways of classifying chemical reactions that have been discussed
in the text
are listed below, along with an example of each type of reaction:
Formation of a solid (precipitation):
FeCl3(aq) + 3NaOH(aq) Fe(OH)3(s) + 3NaCl(aq)
Formation of water (acid–base):
H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l)
Transfer of electrons (oxidation–reduction):
2Na(s) + Cl2(g) 2NaCl(s)
Combustion:
2C2H6(g) + 7O2(g) 4CO2(g) + 6H2O(g) + energy
Synthesis (combination):
Ca(s) + Cl2(g) CaCl2(s)
Decomposition:
2HgO(s) 2Hg(l) + O2(g)
Single displacement:
Mg(s) + 2AgNO3(aq) Mg(NO3)2(aq) + 2Ag(s)
Double displacement:
Na2SO4(aq) + BaCl2(aq) 2NaCl(aq) + BaSO4(s)