What is the acid concentration of a sample of acid rain with a pH of 4.20? Chemistry Acids and Bases pH calculations 1 Answer Junaid Mirza Nov 13, 2016 #6.3times10^-5#mol/L Explanation: #pH=-log_10[H^+]# Given that #pH# is 4.2 #:. 4.2=-log_10[H+]# #10^(-4.2)=[H^+]# Taking antilog we get #[H^+]=6.3times10^(-5)# mol/L Answer link Related questions How do you determine ph of a solution? How do you determine pH at an equivalence point? How do you determine pH from molarity? What does alkalinity mean? What is a base? How do acid base indicators change color? What is a neutral pH? How does alkalinity affect pool water? Why is pH important in drinking water? How can I calculate the pH of a solution? See all questions in pH calculations Impact of this question 10292 views around the world You can reuse this answer Creative Commons License