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.

Answer 1

Correct Answer - a) `1.5 xx 10^(-7) M` , b) `10^(-5) M` , c) `6.31 xx 10^(-5) M` , d) `6.31 xx 10^(-3) M`
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^(+)] = "antilog" (-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^(+)] = "antilog" (-5.0)`
`10^(-5) M`
(iii) pH pf tomato juice `= 4.2`
Since, `pH = -"log" [H^(+)]`
`4.2 = - "log" [H^(+)]`
`"log" [H^(+)] = -4.2`
`[H^(+)] = "antilog"(-4.2)`
`= 6.31 xx 10^(-5) M`
pH of lemon juice `= 2.2`
Since, `pH = - "log"[H^(+)]`
`2.2 = - "log" [H^(+)]`
`"log" [H^(+)] = -2.2`
`[H^(+)] = "antilog" (-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^(+)] = "antilog" (-7.8)`
`= 1.58 xx 10^(-8) M`