The concentration of hydronium ions in a cup of black coffee is 1.3 × 10-5 M. What will be the pH of the coffee?

Question

The concentration of hydronium ions in a cup of black coffee is 1.3 × 10-5 M. What will be the pH of the coffee? (A) 4.89 (B) 3.89 (C) 2.20 (D) None of these

Tardigrade Admin · Accepted Answer

Given, [H3 O+]=1.3 × 10-5 ∵ p H=- log [H3 O+] =- log (1.3 × 10-5) =-( log 1.3+ log 10-5) =-0.1139+5 ∴ p H=4.886 ≈ 4.89

Q. The concentration of hydronium ions in a cup of black coffee is $1.3 \times 1 0^{- 5} M$ . What will be the $p H$ of the coffee?

4.89

3.89

2.20

None of these

Given, $[H_{3} O^{+}] = 1.3 \times 1 0^{- 5}$
$∵ p H = - lo g [H_{3} O^{+}]$
$= - lo g (1.3 \times 1 0^{- 5})$
$= - (lo g 1.3 + lo g 1 0^{- 5})$
$= - 0.1139 + 5$
$∴ p H = 4.886 \approx 4.89$

Q. The concentration of hydronium ions in a cup of black coffee is 1.3×10−5M. What will be the pH of the coffee?