The pH of black coffee is 5.1. What is the pH of a substance that is 40 times less acidic than black coffee? Round your answer to 2 decimal places.

Answer 1

pH is the negative log of the hydrogen ion concentration

less acidic means higher pH

5.1 + log(40) = ?

Answer 2

I was taught the formula pH = -log[H+]. Isn't H+ the hydronium ion concentration? So why do we replace it with 40? I wasn't told what the argument for the log is