Answers
 

Question	Answer	Question	Answer
88	4	92	1
89	2	93	2
90	3	94	4
91	5

 

Explanation

pH follows on directly from the previous section on log₁₀ scales. pH = - log₁₀ [H⁺].
Thus when [H⁺] = 10^-4M, pH = 4. When [H⁺] = 4 × 10^-4M, pH = between 3 and 4. (Q 88). This is due to 10^-3 > 4 × 10^-4 > 10^-4.
Remember that strong acids such as HCl and H₂SO₄ dissociate fully, so that a solution of 4 mmol of HCl per litre has a [H⁺] = 4 × 10^-3 M (thus pH between 2 and 3. Q90). A solution of 0.5 mol.l^-1 H₂SO₄ will dissociate to give a [H⁺] = 1 mol.l^-1 (thus a pH = 0. Q93)