CH40S
Acid-Base Equilibria Review Key
1. HZ
2.a) Strong acids/bases completely dissociate, whereas weak acids/bases only partially
dissociate.
b) Concentrated means that there is a high molarity (e.g. dissolved in a small amount of water),
whereas dilute means that there is a low molarity (e.g. dissolved in a large amount of water).
3. Yes, the acid could be dissolved in a small amount of water but still only partially dissociate.
4. NaHCO3 + HCl  NaCl + H2CO3
Since HCl is a stronger acid than H2CO3, the reaction will be product favoured since HCl is more
likely to donate H+.
5.  NH4+ + HS–
H2S is a stronger acid than NH4+, therefore it donates more H+, so rxn is product
favoured.
6. a) Equilibrium will shift to the right (shift to the product side) because the OH– of the NaOH
will combine with the H3O+ to form water, this rxn between the hydroxide and hydronium ion
reduces the concentration of the hydronium ion.
b) Equilibrium will shift to the left (shift to the reactant side) because the H+ (actually H3O+
because it’s in an aqueous solution) of the HCl will cause the concentration of H3O+, in the
reaction listed, to increase.
7. [H+] and [HS–] = 2.24x10–4 mol/L
[H2S] = 0.49998 or 0.5 mol/L
pH = 3.65
% diss. = 0.045%
**** need to use Ka value from Ka table
8. Ka = 1.33x10–7
9.(HClO4 is a strong acid, so ….) [H+] 4.and [ClO4–] = 4x10–3 mol/L, pH=2.40
10. 4.2x10–4 mol/L
11. 0.0267 L
12. 0.0125 L
13. 200g
14. [H3O+] = 2.51x10–5 mol/L, [OH–]=3.98x10–10 mol/L
15.(****Ka is not required for answer… tricky!) [H3O+] =9x10–5 and pH= 4.05
16.% diss = 0.0325%
17. Ka=9.09x10–10
18. [H+]=8.66x10–5 mol/L, pH=4.06, pOH=9.94
19.  C2O42– + H2CO3
b) Equilibrium favours the products since HC2O4– is a stronger acid than H2CO3
20. Ka = 1.33x10–7
21. (*** must Ka from Ka table)
a) [H3O+] = 0.016 mol/L
b) pH=1.80
c)% diss. = 3.19%
22. omit (compound formula was typed incorrectly)
23. 0.044L
24. 0.8g NaOH
25. a) Acids:
An acid is a substance that releases H+ ions in water.
Eg) HCl(aq)  H+(aq) + Cl-(aq)
Bases :
A base is a substance that releases OH- ions in water.
Eg) NaOH(aq)  Na+(aq) + OH-(aq)
b) An acid is a proton (H+) donor, and a base is a proton acceptor
acid e.g. HCl + H2O  H3O+ + Cl–
base e.g. NH3 + H2O  NH4+ + OH–
c) An acid accepts an electron pair during a reaction, a base donates an electron pair during a
reaction.
Acid e.g AlCl3
Base e.g. NH3