Question

What is the concentration of hydrogen ions [H+] in a solution of pH = 4.0?
1 × 104M
4 × 10–4M
2 × 10–2M
1 × 10–4M

Answer 1

all we need to do is used the following formula:

[H+] = 10^-pH

so

[H+]= 10^-4.0= 1 x 10^-4 M
the answer is the last choice

Answer 2

Answer: $1\times 10^{-4}M$

Explanation:

pH or pOH is the measure of acidity or alkalinity of a solution.

pH is calculated by taking negative logarithm of hydrogen ion concentration and pOH is calculated by taking negative logarithm of hydroxide ion concentration.

$pH=-\log [H^+]$

$pOH=-log[OH^-]$

$pH+pOH=14$

Given: pH= 4.0

Putting in the values in the given equation:

$4.0=-\log [H^+]$

$[H^+]=1\times 10^{-4}M$

Thus concentration of hydrogen ions [H+] in a solution of pH = 4.0 is $1\times 10^{-4}M$