A 1.5L sample of water taken from a pond contains 9.0 x 10^19 H+ ions, what is the pH of the sample?

Question

I tried to figure it out but keep getting the wrong answer if anyone out there can show me step by step how to solve this problem I would greatly appreciate it.

Answer 1

"1.5L of water contains 9.0x10^19 H+" is equivalent to "1.0L of water contains 6.0x10^19 H+", which is equivalent to "1.0L of water contains (6.0x10^19)/(6.022x10^23) = 9.96x10^-5 M H+".
That is to say: [H+] = 9.96x10^-5 M
pH = - log[H+] = 4.0