Question

The equation for the pH of a substance is pH = –log[H+], where H+ is the concentration of hydrogen ions. A basic solution has a pH of 11.2. An acidic solution has a pH of 2.4. What is the approximate difference in the concentration of hydrogen ions between the two solutions? a) 1.6*10^-9 b) 4.0*10^-3 c)6.7*10^-1 D)1.6*10^-1

Answer 1

PH=-log[H⁺]

First solution:
PH=11.2

11.2=-log[H⁺]

log[H⁺]=-11.2
[H⁺]=10⁻¹¹.²=6.0309⁻¹²


Second solution:
PH=2.4

2.4=-log[H⁺]
log[H⁺]=-2.4
[H⁺]=10⁻².⁴=3.98*10⁻³

Difference between the two solutions=3.98*10⁻³ - 6.03*10⁻¹²≈4.0*10⁻³.

Answer: b) 4.0*10⁻³

Answer 2

The correct answer si option (b).

Step-by-step explanation:

`pH = -\log[H+]`

Concentration of hydrogen ions when pH is 11.2.

`11.2=-\log[H^+]`

`[H^+]=6.309* 10^(-12) M`

Concentration of hydrogen ions when pH is 12.4.

`2.4=-\log[H^+]`

`[H^+]'=0.0039810 M=3.9810* 10^(-3) M`

Difference between the hydrogen ions:

`=[H^+]'-[H^+]`

`=0.00398 M-6.309* 10^(-12) M=0.00397 M=3.97* 10^(-3)\approx 4.0* 10^(-3)M`

Hence, the correct answer si option (b).