How many moles of H3O+ must be added to 349 mL of a solution to adjust the pH from 7.40 to 5.33? Use E notatio

Question

I'm totally stuck! I don't even know where to go with this!!! ahhhh!!

well.. i know .347 L is probably important.. and the change of pH is 2.07..??

Answer 1

pH = 7.40 >>[H+] = 10^-7.40 = 4.0 x 10^-8 M
moles H+ = 349 x 4.0 x 10^-8 /1000 = 1.4 x 10^-8

pH = 5.33 >> [H+] = 10^-5.33 = 4.7 x 10^-6 M
moles H+ = 349 x 4.7 x 10^-6 /1000 = 1.64 x 10^-6

1.64 x 10^-6 - 1.4 x 10^-8 = 1.63 x 10^-6 ( moles H+ that we have to add )

Answer 2

10^-5.33-10^-7.4