The hydrogen ion concentrations in cheeses range from 1.00 10-5 M to 1.26 10-7 M. Find the corresponding range of pH readings

Question

1. The hydrogen ion concentrations in cheeses range from 1.00  10^-5 M to 1.26  10^-7 M. Find the corresponding range of pH readings

Answer 1

Hello, Nelson,

pH is defined as the negative log of the hydrogen ion concentration. The log (base 10) of a number is the exponent of 10 raised to a power that would result in that number. For example, the log of 10 is 1 (10¹ = 10), the log of 1 is 0 (10⁰ = 1), log(5) = 0.699, and so forth.

In this case, the conversion is easy because we are going the other way. Find the log of 1x10^-5 and then take the negative of that number. The log of this value is easy (-5). The negative of minus 5 is plus five.

pH = 5

1.26 x 10^-7 is slightly harder. The log of this number is -6.90 (3 sig figs), making the pH 6.90.

I hope this helps,

Bob