CHEM 12
ACID AND BASE UNIT REVIEW
CONCEPTS
1. List the properties of acids (taste sour, conduct electricity, change the colours of indicators, react with
certain metals to produce H2, are neutralized by bases) and bases (taste bitter, conduct electricity, change
the colours of indicators, feel slippery, are neutralized by acids) .
2. What ion is produced when an acid reacts with water? ( H3O+ ) A base? ( OH- )
3. Define: conjugate ( formula that differs by one H+ ), Arhenius acid ( ionizes in water to produce H+ ) and
base ( ionizes in water to produce OH- ), Bronsted acid (proton donor) and base (proton acceptor), weak
acid (an acid that does not completely ionize in water), strong acid (an acid that completely ionizes in
water), ionization (the production of anions and cations), equivalence point of a titration (when the moles
of H+ = the moles OH- ), transition point of an indicator (write an equation) ( When [HInd]=[Ind -] ), buffer (
a solution that will maintain a relatively constant pH that consists of a weak acid or base mixed with the
salt that contains the congugate) and hydrolysis (the reaction of the cation or anion with water as an acid or
a base).
4. Identify the acids or bases in the following equation. Are the reactants or products favoured?
HC03-(base) + HF(stronger acid)<-----> H2CO3(weaker acid) + F-(base)
The products are favoured as the stronger acid is on the left and pushes the reaction to the right.
5. Classify each compound as a strong or weak acid or base; acidic or basic anhydride; acidic, basic, or
neutral salt; or buffer system. Write an equation to show how each reacts with water.
NH3
weak base
SO2 acid
anhydride
AlCl3
acidic
salt
NaF
H2CO3
HClO4
weak acid
strong
acid
HCl
NaI
strong
basic salt
acid
NH3 and NH4Cl buffer
neutral
salt
Al(H2O)6+3 + H2O <--------> Al(H2O)5(OH)+2 + H3O+
HClO4 + H2O --------> H3O+ + ClO4 CN- + H2O <----> HCN + OH-
NH4Cl
basic salt
acidic salt strong base
KOH
NaOH
K2O basic
anhydride
strong
base
NaCH3COO and CH3COOH buffer
NH3 + H2O <----> NH4 + + OH-
H2CO3 + H2O <--------> H3O+ + HCO3 -
KCN
CO2 acid
anhydride
NH4+ + H20 <-------> NH3 + H3O+
KOH -----> K+ + OHSO2 + H2O -----> H2SO3
F- + HOH(l) <-----> HF + OHHCl + H2O --------> H3O+ + Cl NaI --------> Na+ + IK2O + H2O --------> 2KOH
NaOH --------> Na+ + OHCO2 + H2O -----> H2CO3
NH3 + H2O <----> NH4 + + OHCH3COOH + H2O <--------> H3O+ + CH3COO 6. H+is short for ______. H3O+
7. Determine the conjugates for each of the bases.
CN- HCN
NH3 NH4 +
F- HF
OH- H2O
Co(H2O)5(OH)+2 Co(H2O)6+3
8. Determine the conjugates for each of the acids.
HF F-
HCN CN-
Al(H2O)6+3 Al(H2O)5(OH)+2
NH4+ NH3
HPO4-2 PO4-3
9. Describe a strong and weak acid as well as a strong and weak base in terms of each of the following:
Conductivity ( strong acids or bases are good conductors strong while weak acids or bases are poor
conductors )and, Size of Ka or Kb (strong acids or bases have large Kas or Kbs while weak acids or bases
have small Kas or Kbs) , Degree of Ionization (strong acids or bases completely ionize while weak acids or
bases do not completely ionize) and pH (Assuming 1.0M, strong acids pH=0, strong bases pH=14, weak
acids pH>0, weak bases pH<14 ) .
10. Why is the strongest acid in water H3O+? Explain! HCl + H2O <--------> H3O+ + Cl 11. Why is the strongest base in water OH-? Explain! NaOH ----> Na+ + OH-
12. Which has the higher pH H2S03 or H3BO3? Explain!
H3BO3 as it is the weakest acid.
13. Which has the higher pH NaCN or NaF? Explain!
NaCN as it is the strongest base.
14. A buffer has a pH of 9.00. 2 drops of a dilute strong acid are added. Estimate how the pH changes?
It will remain the same or drop slightly.
15. a) Complete the chart by indicating the pairs required to make buffer solutions. For example HCN
(weak acid) and NaCN (salt containing the conjugate of the weak acid) will make a buffer solution. b)
Write an equation the describes the equilibrium for each buffer. c) Circle the formulas that have high
concentrations.
Weak Acid or Base
Salt
HF
NaF
CH3COOH
NaCH3COO
NH3
NH4Cl
HCN
NaCN
H2CO3
NaHCO3
H3PO4
KH2PO4
HCH3COO
NaCH3COO
HF + H2O <--------> H3O+ + F CH3COOH + H2O <--------> H3O+ + CH3COO NH3 + H2O <----> NH4 + + OHHCN + H2O <--------> H3O+ + CN H2CO3 + H2O <--------> H3O+ + HCO3 H3PO4 + H2O <--------> H3O+ + H2PO4 HCH3COO + H2O <--------> H3O+ + CH3COO 16. Match each equation with its type:
Acid/base formula equation
HCl + NaOH ----->NaCl + HOH(l )
Acid/base net ionic equation
H+ + OH- -----> HOH(l)
Solubility product ionization equation
AgCl(s)< -----> Ag+ + Cl-
Hydrolysis of a weak acid
NH4+ + H20 <-------> NH3 + H3O+
Hydrolysis of a weak base
F- + HOH(l) <-----> HF + OH-
Ionization of water
H20(l) <-----> H+ + OH-
17. Write the equilibrium expression for each of the above equations.
Kb=[HF][OH-]/[F- ]
Ksp=[Ag+][Cl-]
Kw=[ H+ ][OH-]
Ka=[NH3 ][H3O+/[NH4+ ]
18. A student tested the electrical conductivity of two acid solutions. One solution was a strong acid and the
other a weak acid. Both solutions had the same conductivity. Explain how this could be possible.
The strong acid was dilute and the weak acid was concentrated.
19. Describe in terms of hydrolysis how NaCH3COO can be added to potato chips in order to produce the
vinegar flavour. CH3COO- + H2O <--------> CH3COOH + OH- the acetate ion hydrolyzes with the water in
your mouth to produce vinegar (CH3COOH ).
20. Describe what happens to the H+ and the OH- when the pH increases by 2 units.
[H+] decreases by a factor of 100. [OH- ] increases by a factor of 100.
21. Describe two gases responsible for acid rain. SO2 or SO3 and NO2 Write aquations to show how they
react with water. SO2 + H2O -----> H2SO3 or SO3 + H2O -----> H2SO4
2NO2 + H2O------> HNO3 + HNO2What gas naturally lowers the pH of normal rain? CO2
22. Complete the following reaction using a formula equation, complete ionic equation and net ionic
equation.
H2C2O4 + 2NaOH ----->Na2C2O4 + 2H2O
H2C2O4 + 2Na+ + 2OH- -------> 2Na+ + C2O4-2 + 2H2O
H2C2O4 + 2OH- -------> C2O4-2 + 2H2O
23. Write the equilibrium expression for phosphoric acid in water. H3PO4 <----> H+ + H2PO424.
a) An indicator HInd is red in acid and blue in base. Write
the equation for the indicator and explain the colours.
HInd(red) + H2O <-----> H3O+ + Ind-(blue)
When [HInd] =[Ind-] the color is orange
b) What is true at the transition point?
[HInd]=[Ind-] and Ka = [H3O+ ]
c)What is the color of this indicator in a solution of AlCl3?
-
AlCl3 is an acid salt- indicator is red.
d) In the above solution, what is larger [HInd] or [Ind ] ?
[HInd] > [Ind-]
e) Calculate the Ka for Phenolphthalein.
8 X 10-10
f) What indicator has a Ka of approximately 1.0 X 10 -10?
Thymolpthalein
25. Give an example of a monoprotic HCl → H+ + Cl-, diprotic H2SO4 → H+ + HSO4-1 , and triprotic
acid H3PO4 ⇌ H+ + H2PO4-1. Write an equation for each to show how they ionize in water.
26. Give the approximate pH of the equivalence for each titration. Choose an appropriate indicator.
Acid
Base
HCl
NaOH 7
H2SO4 NH3
HF
pH of Equvalence Point Indicator
Bromo thymol blue
5
Methyl Red
KOH 9
Phenolpthalein
27. Which of the following will have the lowest pH?
HCLO HClO2 HClO3 HClO4 Strongest acid more O's &lowest pH
28. Pick a formula that is amphriprotic. Formulas in red can both gain or lose a proton.
F-
H2SO4 H20
HCO3-
CO3-2 KOH H2PO4- HPO4-2
CALCULATIONS
1. Calculate the quantities required to complete the table. In the first row write the general equations for
each quantity. Watch your significant figures.
[H+] = 10-pH
[OH-] = 10-pOH pH = -Log[H+] pOH = -Log[OH-]
[H+]
[OH-]
pH
pOH
Acid/base/neutral
5.0 x 10-3 M
2.0 x 10-12 M
2.30
11.70
acid
-5
7.7 x 10-10 M
1.3 x 10 M
9.11
4.89
basic
8 x 10-4 M
1 x 10-11 M
3.1
10.9
acid
11.492
2.508
basic
7.00
7.00
neutral (2sig figs)
3.22 x 10
-12
-7
-3
M 3.10 x 10 M
1.0 x 10 M
-7
1.0 x 10 M
2. What volume of .20M H2SO4 is needed to neutralize 50.00 ml .30M NaOH? 0.038L
3. What mass of NaF is required to prepare 100ml of .300M solution? 1.26g
4. 35.5 ml of .300M NaOH is required to neutralize 10.0 ml of H 2SO4. What is the acid concentration?
.533M
5. 100 ml of .200 M HCl is mixed with 120ml of .200M NaOH. Calculate the pH of the resulting solution.
pH=12.26
6. Calculate the Ka for phenolpthalein. 8x10-10
7. The Ksp of AgOH is 6.8x10-12. Calculate the pH. pH=8.42
8. The OH- concentration in .10M NaCN is 2.7x10-6M. Calculate the Kb from this information only.
Kb=7.3x10-11
9. Calculate the pH for .20M HCl. pH= 0.70
10. Calculate the pH for .10M Ba(OH)2. pH=13.30
11. Calculate the pH for .40M HCN. pH=4.85
12. Calculate the pH for .40M Na2CO3. pH=11.93
13. What is the pH for .30M NaCl? pH=7.00
14. Calculate the pH of .20M NH3. pH=11.28
15. Calculate the pH of .20M NH4Cl. pH=4.98
16. Show by calculation if H2PO4- is an acid or base (compare the Kb and Ka).
Ka (H2PO4- ) =6.2x10-8> Kb (H2PO4- ) =1.3x10-12 therefore an acid
17. Calculate the pH of a saturated solution of Mg(OH)2 if the Ksp is 1.2 X 10-11. pH = 10.46
18. A .50M NH3 solution is found to have a OH- concentration of 1.86 x 10-3 M. Using this data only
calculate the Kb. 6.9 x 10-6
19. A .18M acid HX has a pH of 2.40. What is the Ka? 9.0 x 10-5
20. The following data were recorded when 25.00ml of H 2SO4 were titrated with .1030M NaOH. The
volumes of NaOH used in three runs were: 46.06ml, 44.52ml, 44.54ml. Calculate the acid concentation.
9.173 x 10-2 M
21. The following data were recorded when 10.00ml of NaOH were titrated with .1030M H 2SO4. The
volumes of H2SO4 used in three runs were: 12.55ml, 12.55ml, 12.10ml. Calculate the base concentration.
0.2585 M