6B.9

[Ricky Ma DIS 4E]

(i), when i divide 1.0x10^-14/1.50 to get concentration of OH-, i get 6.667x10^-15 but the solution manual says the answer is 1.5x10^14. I tried to work backwards from the other values given in the table and it seems that the issue is the 1.50 molar concentration given in the table. Am I not seeing something? 10^-0.176 isnt even equal to 1.50 molar concentration.THanks!

[Sarah Fatkin 4I]

Hi! To find the concentration of OH- you need to take the -log[H30+] then take the difference between that and 14 to find pOH. Then raise 10^(-pOH) to find [OH-]. This gives you 1.50*10^-14. Hope this helps!

[Matthew Tran 1H]

Actually, I think the solutions manual is wrong on this problem, and 6.667x10^-15 is correct. Since [H3O+]=1.50M which is greater than 1M (pH=0), the solution will have a negative pH (-0.176). When you were checking your work, you did 10^-0.176, but you should have done 10^0.176 because [H3O+]=10^-pH. Subsequently, the pOH will be greater than 14 since the pH is negative. The same concept applies to the second row. Hope this helps!