```Honors Chemistry
Ka, Kb and Neutralization Rxns.
1. Describe the difference between a weak acid and a strong acid. Give an example of each.

weak acids partially ionizes in solution, whereas strong acids completely ionize in solution. Weak acid:
HC2H3O2 (acetic acid), H2S (hydrosulfic acid). Strong acid: HNO3 (nitric acid), HCl (hydrochloric acid.)
2. Describe the difference between a weak base and a strong base. Give an example of each.

weak base partially dissociates in solution and a strong base completely dissociates in solution. Weak base:
NH3 ( ammonia), HCO3- (bicarbonate). Strong base: NaOH (sodium hydroxide), KOH (potassium hydroxide.)
3. Define the symbol Ka and Kb.

Ka is the acid ionization constant and it is the ratio of the concentrations of the products divided by the
[+][−]
reactants for an acid. If Ka>1 then it is a strong acid and < 1 a weak acid.  = [} . Kb is the equivalent
relationship for bases.
4. The concentration H+ in a HF acid solution is 1.0 x 10-4 M and the amount of undissociated (not
ionized) Hydroflouric Acid, HF, is 2.5 x 10-6 M. What is the dissociation constant for this acid? Is this
considered to be a strong or weak acid?

+
−
() ⟶ ()
+ ()
=
[+][−]
(1  10−4 )(1  10−4 )
[}
2.5 10−6
=
= .004
therefore weak acid
5. Acetic Acid is the conjugate acid of the acetate anion. It is a weak monoprotic acid that dissociates to
an acetate ion and a hydrogen ion in aqueous solution. Calculate Ka for acetic acid if a 1.0 M solution
results in an equilibrium [H+] =0.0042 M.

+
2 3 2 ⟶ ()
+ 2 3 2 −
()
=
[+][−]
(.0042).0042)
[}
1.0
=
= 1.76  10−5
therefore weak acid
6. Ammonia is a weak base. If the initial concentration of ammonia is 0.150 M and the equilibrium
concentration of OH- is 1.6 x 10-3 M, calculate Kb for ammonia.

−
3 ⟶ 4 +
() + ()
=
[−][+]
(1.6  10−3 )(1.6  10−3 )
[]
0.150
=
= 1.71  10−5
therefore weak
base
7. At 37°C, which is normal body temperature, Kw = 2.4 x 10-14. Calculate [H+] and [OH-] in a neutral
solution at this temperature.
  = [ +][−]
2.4 x 10-14 = [H+][OH-]
2.4 x 10-14 = x2
= 1.55 x 10-7 M
8. At 50°C, Kw = 5.47 x 10-14. Calculate [H+] and [OH-] in a neutral solution at this temperature.
  = [ +][−]
5.47 x 10-14 = [H+][OH-]
5.47 x 10-14 = x2
= 2.34 x 10-7 M
9. A 0.010 M solution of aspirin, a weak monoprotic acid, has a pH of 3.3. What is the Ka of aspirin?

= − log[ + ]
3.3 = −log[ + ]
10−3.3 = 5.01  10−4
=
(5.01  10−4 )(5.01  10−4 )
0.010
= 2.51  10−5
10. A 0.513 M solution of a weak base has a pH of 11.4. What is the Kb of the base?

+  = 14
= −log(−)
pOH=14-11.4
pOH= 2.6
2.6 = −log( − )
10−2.6 = .0025
=
(.0025).0025)
0.153
= 4.08  10−5
11. Formic acid is a weak monoprotic acid that is partly responsible for the irritation of insect bites. If the
initial concentration of formic acid is 0.1 M and the equilibrium concentration of both the H+ and the
conjugate base are 4.2 x 10-3, calculate Ka for formic acid.

=
(4.2  10−3 )(4.2  10−3 )
0.1
= 1.76  10−4
12. The acetate ion is a very weak base. If the initial concentration of acetate ion in solution is 0.1 M, and
the equilibrium concentration of OH- is 7.5 x 10-6 M, calculate Kb for the acetate ion.

=
(7.5  10−6 )(7.5  10−6 )
0.1
= 5.63  10−10
13. How many moles of LiOH are needed to exactly neutralize 2.0 moles of H2SO4?
 H2SO4(aq) + 2LiOH(aq) ⟶ 2H2O(l) + Li2SO4(aq)
2.0  2 4 ×
2
= 4.0
1  2 4
14. How many moles of H2SO4 are needed to neutralize 5.0 moles of NaOH?
 H2SO4(aq) + 2NaOH(aq) ⟶ 2H2O(l) + Na2SO4(aq)
5.0   ×
1  2 4
= 2.5  2 4
2
15. How many moles of HCL are needed to neutralize 0.10 L of 2.0 M NaOH?
 HCl(aq) + NaOH(aq) ⟶ H2O(l) + NaCl(aq)
2.0
1
0.10
×
×
= 0.2
1
1
1
16. How many moles of NaOH are needed to neutralize 0.010 L of 0.20 M H2SO4?
H2SO4(aq) + 2NaOH(aq) ⟶ 2H2O(l) + Na2SO4(aq)
0.20  2 4 2   0.10
×
×
= 0.04
1
1  2 4
1
17. If it takes 15.0 mL of 0.40 M NaOH to neutralize 5.0 mL of HCl, what is the molar concentration of the
HCl solution?
 HCl(aq) + NaOH(aq) ⟶ H2O(l) + NaCl(aq)
0.40
1
0.015
1
×
×
×
= 1.2
1
1
1
0.005
18. If it takes 10.0 mL of 2.0 M H2SO4 to neutralize 30.0 mL of KOH, what is the molar concentration of the
KOH?
 H2SO4(aq) + 2KOH(aq) ⟶ 2H2O(l) + K2SO4(aq)
2.0  2 4
2
0.010
1
×
×
×
= 1.33
1
1  2 4
1
0.030
19. How many mL of 2.0 M H2SO4 are required to neutralize 30.0 mL of 1.0 M NaOH?
 H2SO4(aq) + 2NaOH(aq) ⟶ 2H2O(l) + Na2SO4(aq)
1.0
1  2 4 0.03
1
×
×
×
= .0075   7.5
1
2
1
2.0  2 4
20. How many mL of 0.10 M Ca(OH)2 are required to neutralize 25.0 mL of 0.50 M HNO3?
 2HNO3(aq) +Ca(OH)2(aq) ⟶ 2H2O(l) + Ca(NO3)2(aq)
0.5  3
1  ()2 0.025
1
×
×
×
= .0625   62.5
1
2  3
1
0.1  ()2
```