#### Question

The pH of milk, black coffee, tomato juice, lemon juice and egg white are 6.8, 5.0, 4.2, 2.2 and 7.8 respectively. Calculate corresponding hydrogen ion concentration in each.

#### Solution

The hydrogen ion concentration in the given substances can be calculated by using the given relation:

pH = –log [H^{+}]

(i) pH of milk = 6.8

Since, pH = –log [H^{+}]

6.8 = –log [H^{+}]

log [H^{+}] = –6.8

[H^{+}] = anitlog(–6.8)

`= 1.5 xx 10^(-7) M`

(ii) pH of black coffee = 5.0

Since, pH = –log [H^{+}]

5.0 = –log [H^{+}]

log [H^{+}] = –5.0

[H^{+}] = anitlog(–5.0)

`= 10^(-5) M`

(iii) pH of tomato juice = 4.2

Since, pH = –log [H^{+}]

4.2 = –log [H^{+}]

log [H^{+}] = –4.2

[H^{+}] = anitlog(–4.2)

`= 6.31 xx 10^(-5) M`

iv) pH of lemon juice = 2.2

Since, pH = –log [H^{+}]

2.2 = –log [H^{+}]

log [H^{+}] = –2.2

[H^{+}] = anitlog(–2.2)

`= 6.31 xx 10^(-3) M`

(v) pH of egg white = 7.8

Since, pH = –log [H^{+}]

7.8 = –log [H^{+}]

log [H^{+}] = –7.8

[H^{+}] = anitlog(–7.8)

`= 1.58 xx 10^(-8) M`