1. Baking soda may serve as a source of CO2 in bread dough. It causes the
dough to raise. The CO2 is released when NaHCO3 reacts with an acidic
substance:
NaHCO3(aq) + H+(aq) → Na+(aq) + H2O(l) + CO2(g)
Classify the reaction as redox or nonredox
Non-redox there are no changes in oxidation number.
2. Consider all of the following ionic compounds to be water soluble and write
the formulas of the ions that would be formed if the compounds were
dissolved in water. Table 4.7 will be helpful.
a) K2Cr2O7 b) H2SO4 c) NaH2PO4 d) Na3PO4 e) NH4Cl f) KMnO4
(a) K+, Cr2O72-(b) H+, SO42-, (c) Na+, H+, PO43-, (d) Na+, PO43- (e) NH4+, Cl(f) K+, MnO4-
3. Reactions represented by the following equations take place in water
solutions. Write each full equation in total ionic form, then identify spectator
ions and write the equations in net ionic form. Solids that do not dissolve are
designated by (s); and gases that do not dissolve are designated by (g); and
those substances that dissolve but do not dissociate are underlined.
a. H2O(l) + Na2SO3(aq) + SO2(aq) → 2NaHSO2(aq)
b. 3Cu(s) + 8HNO3(aq) → 3Cu(NO3)2(aq) + 2NO(g) + 4H2O(l)
c. 2HCl(aq) + CaO(s) → CaCl2(aq) + CO2(g) + H2O(l)
d. CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
e. MnO2(s) + 4HCl(aq) → MnCl2(aq) + Cl2(aq) + 2H2O(l)
f. 2AgNO3(aq) + Cu(s) → Cu(NO3)2(aq) + 2Ag(s)
(a) total ionic equation:
H2O(l) + 2Na+ + SO32-(aq) + SO2(aq) → 2Na+(aq) + 2HSO2-(aq)
Or
H2O(l) + 2Na+ + SO32-(aq) + SO2(aq) → 2Na+(aq) + 2H+ + 2SO2-(aq)
spectator ions (we will consider the only the second option):
Na+
net ionic equation:
H2O(l) + SO32-(aq) + SO2(aq) → 2H+ + 2SO2-(aq)
(b) total ionic equation:
3Cu(s) + 8H+(aq) + 8NO3-(aq) → 3Cu2+(aq) + 6NO3-(aq) + 2NO(g) + 4H2O(l)
spectator ions:
NO3net ionic equation:
3Cu(s) + 8H+(aq) + 2NO3-(aq) → 3Cu2+(aq) + 2NO(g) + 4H2O(l)
(c) Equation doesn’t agree with Law of Conservation of Mass !! No
carbon on reactants side.
(d) total ionic equation:
Ca2+(aq) + CO32-(s) + 2H+(aq) + 2Cl-(aq) → Ca2+(aq) + 2Cl-(aq) + CO2(g) + H2O(l)
spectator ions:
Cl-, Ca2+
net ionic equation:
CO32-(s) + 2H+(aq) → CO2(g) + H2O(l)
(e) total ionic equation:
MnO2(s) + 4H+(aq) + 4Cl-(aq) → Mn2+ + 2Cl-(aq) + Cl2(aq) + 2H2O(l)
spectator ions:
Clnet ionic equation:
MnO2(s) + 4H+(aq) + 2Cl-(aq) → Mn2+ + Cl2(aq) + 2H2O(l)
(f) total ionic equation:
2Ag+(aq) + 2NO3-(aq) + Cu(s) → Cu2+ + 2NO3-(aq) + 2Ag(s)
spectator ions:
NO3net ionic equation:
2Ag+(aq) + Cu(s) → Cu2+ + 2Ag(s)
4. The following molecular equations all represent neutralization reactions of
acids and bases. These reactions are discussed further in Chapter 9. Write
each equation in total ionic form, identify the spectator ions, then write the net
ionic equation. Water is the only substance that does not dissociate. What do
you notice about all the net ionic equations?
a. HBr(aq) + RbOH(aq) → RbBr(aq) + H2O(l)
b. H2SO4(aq) + 2LiOH(aq) → Li2SO4(aq) + 2H2O(l)
c. HCl(aq) + CsOH(aq) → CsCl(aq) + H2O(l)
(a) total ionic equation:
H+(aq) + Br-(aq) + Rb+(aq) + OH-(aq) → Rb+(aq) + Br-(aq) + H2O(l)
spectator ions:
Rb+, Brnet ionic equation:
H+(aq) + OH-(aq) → H2O(l)
(b) total ionic equation:
2H+(aq) + SO42-(aq) + 2Li+(aq) + 2OH-(aq) → 2Li + SO42-(aq) + 2H2O(l)
spectator ions:
Li+, SO42net ionic equation:
H+(aq) + OH-(aq) → H2O(l)
(c) total ionic equation:
2H+(aq) + SO42-(aq) + 2Li+(aq) + 2OH-(aq) → 2Li + SO42-(aq) + 2H2O(l)
spectator ions:
Li+, SO42net ionic equation:
H+(aq) + OH-(aq) → H2O(l)
5. In refrigeration systems, the area to be cooled has pipes running through it.
Inside the pipes, a liquid evaporates and becomes a gas. Is the evaporation
process exothermic or endothermic? Explain.
The reaction of a liquid becoming a gas is an endothermic process, as it
requires energy to move the particles of the liquid further enough apart
to become a gas and this energy comes from the surroundings.
Endothermic processes remove heat from the surroundings resulting in
them becoming cooler.
6. Calculate the number of grams of SO2 that must react to produce 350 g
SO3. Use the equation from and statements written in Exercise 5.40 and
express your answer using the correct number of significant figures.
7. In Exercise 5.17, you were given an equation for the reaction used to clean
tarnish from silver. The equation for the reaction is:
3Ag2S(s) + 2Al(s) → 6Ag(s) + Al2S3(s)
a) How many grams of aluminum would need to react to remove 0.250 g Ag2S
tarnish?
b) How many moles of Al2S3 would be produced by the reaction described in
part a?
8. An important metabolic process of the body is the oxidation of glucose to
water and carbon dioxide. The equation for the reaction is:
C6H12O6(aq) + 6O2(aq) → 6CO2(aq) + 6H2O(l)
a) What mass of water in grams is produced when the body oxidizes 1.00 mol
of glucose?
b) How many grams of oxygen are needed to oxidize 1.00 mol of glucose?
(a) 1.00 mol glucose produces 6.00 mol of H2O
m = n/M = 6.00/(1.0079x2 + 15.9999)
= 0.333 g of H2O
(b) To oxidze 1.00 mol of glucose 6.00 mol of O2 are required
m = n/M = 6.00/(15.999x2)
= 0.0623 g of O2 required