Which has the greater concentration of hydrogen ions, a substance with a pH of 5 or a substance with a pH of 4?

pH 4

Explanation:

Firstly, we define pH as the negative logarithm to base 10 of the concentration of hydrogen ions.

Mathematically, we express this as:

pH = - log[H+]

Now let's us calculate the concentration of hydrogen in each of the pH

For pH 4, we have:

4 = - log[H+]

[H+] = - Antilog (4)

[H+] = 0.0001M

For pH 5,

[H+] = - Antilog (5)

[H+] = 0.00001M

We can see that 0.0001 is greater than 0.00001 and thus it has a greater concentration of hydrogen ions