what is the [H3O+] if the solution has a hydroxide ion concentration of 2.0 x 10(e-5) {neg. 5exponent}M?

Question

what is the [H3O+] if the solution has a hydroxide ion concentration of 2.0 x 10(e-5) {neg. 5exponent} M?
1) 6.0 x 10(e23)M
2) 5.0 x 10(e-10)M
3) 2.0 x 10(e-7)M
4) 2.0 x 10(e-9)M

Answer 1

Start with the following "fact" (formula):

-log[H30+] + -log[OH-] = 14

Substitue the OH- concentration into the above formula and solve for [H3O+]:

-log[H3O+] - log [2.0 x 10^-5] = 14
-log[H3O+] - (-4.7) = 14
-log[H3O+] = 9.3
log[H3O+] = -9.3
[H3O+] = 5.0 x 10^-10

Therefore, (2) is the correct answer.

Answer 2

For ANY water solution the product of the hydronium ion concentration and the hydroxide ion concentration is 1X10^-14. So, divide that by your hydroxide ion concentration, and you have your answer.

Answer 3

b. 1x 10^-5 mol/L its because in aqueous answer, (H2O) will divided into H+ (hydrogen/proton) and OH-(hydroxyde) with an same concentration.it is also make water pH is 7.00 :)