Acids and Bases Exercises
18.1.4 – 18.1.6
CALCULATIONS INVOLVING ACIDS AND BASES
Review of Important formulas
pH = ‐ log10[H+] [H+] = 10‐pH pKa = ‐ log10 Ka Ka = 10‐pKa pOH = ‐ log10[OH‐] [OH‐] = 10‐pOH pKb = ‐ log10 Kb Kb = 10‐pKb
The ionic product of water = Kw = [H+] x [OH‐] = 1.0 x 10‐14 mol2 dm‐6 at 298 K
The expression varies with temperature pH + pOH = 14 Ka x Kb = 1.0 x 10‐14 pKa + pKb = 14
Acids
The Ka is the acid dissociation constant and is a measure of the strength of an acid or in other words a measure of the ability of an acid to dissociate into ions Complete the table and statements below
Ka pKa 1 x 10‐3
9.4
‐5
1 x 10
9.2 • Compared to a weak acid, a strong acid will contain a __________ concentration of
H+ ions, have a __________ Ka, a __________ pKa and according to Bronsted‐Lowry theory a __________ conjugate base.
•
In comparison, a weak acid will contain a lower concentration of __________ ions, have a small __________, a large pKa and a __________ conjugate base.
1
•
When the strength of the acid decreases the Ka __________ and the pKa
__________.
The following generalized equation is often used to show the dissociation of an acid in water: ⇔
HA(aq)
H+(aq)
+
A‐(aq) general acid conjugate base Ka
=
[H+(aq)] x
[A‐(aq)]
[HA(aq)] Note: that water is not included as one of the reactants in the equation because it is a pure liquid and so its concentration cannot be determined. 1.
Strong Acids
• A strong acid completely dissociates into ions. Therefore we make the approximation (assumption) that the concentration of the acid
CALCULATIONS INVOLVING ACIDS AND BASES
Review of Important formulas
pH = ‐ log10[H+] [H+] = 10‐pH pKa = ‐ log10 Ka Ka = 10‐pKa pOH = ‐ log10[OH‐] [OH‐] = 10‐pOH pKb = ‐ log10 Kb Kb = 10‐pKb
The ionic product of water = Kw = [H+] x [OH‐] = 1.0 x 10‐14 mol2 dm‐6 at 298 K
The expression varies with temperature pH + pOH = 14 Ka x Kb = 1.0 x 10‐14 pKa + pKb = 14
Acids
The Ka is the acid dissociation constant and is a measure of the strength of an acid or in other words a measure of the ability of an acid to dissociate into ions Complete the table and statements below
Ka pKa 1 x 10‐3
9.4
‐5
1 x 10
9.2 • Compared to a weak acid, a strong acid will contain a __________ concentration of
H+ ions, have a __________ Ka, a __________ pKa and according to Bronsted‐Lowry theory a __________ conjugate base.
•
In comparison, a weak acid will contain a lower concentration of __________ ions, have a small __________, a large pKa and a __________ conjugate base.
1
•
When the strength of the acid decreases the Ka __________ and the pKa
__________.
The following generalized equation is often used to show the dissociation of an acid in water: ⇔
HA(aq)
H+(aq)
+
A‐(aq) general acid conjugate base Ka
=
[H+(aq)] x
[A‐(aq)]
[HA(aq)] Note: that water is not included as one of the reactants in the equation because it is a pure liquid and so its concentration cannot be determined. 1.
Strong Acids
• A strong acid completely dissociates into ions. Therefore we make the approximation (assumption) that the concentration of the acid