Posted by **Cliff** on Monday, December 13, 2010 at 10:45pm.

Hi,

I'm trying to solve some chemistry problems, like the ones my teacher says will appear on our exams.

The problem reads like this:

What is the hydrogen conentration in a bleach sample that register 9.55 using a pH meter?

My Attempt:

Since this sample register a 9.55 on a pH meter,it occurs to me that this sample is basic, and I can use the formula:

pOH = -log (H^+), to solve for (OH^-)

=-log(9.55)

=-0.980

From here I thought,maybe if I substitute that result into the equation pH + pOH = 14, I might arrive at the answer I'm looking for; which is 0 000 000 000 35 M.

pH + 0.980 = 14

pH = 13.02

Evidently I took the wrong approach.

Can you help me with this problem?

Have a Great Night

- Chemistry -
**pranav**, Monday, December 13, 2010 at 11:04pm
i did not exactly get that answer... but i still think this will helps. i did 10^pH formula. i got 2.818 x 10^-10 as my naswer. i toke that and divided it by the molar mass of blaech. i got the answer 3.78 x 10^12... which is simalr to your answer

- Chemistry -
**DrBob222**, Monday, December 13, 2010 at 11:12pm
I think you are trying to make this far more difficult that it is. Also, I think your prof gave you the wrong answer (or you've state something wrong or copied something wrong).

if pH = 9.55, then

pH = -log(H^+)

9.55 = -log)H^+)

-9.55 = log(H^+)

(H^+) = 2.82E-9M

(the OH^- is 3.5E-5M

(You should know your answer of pH = 13.02 isn't right. the PROBLEM states pH = 9.55 and not 13.02.

By the way, pOH = -log(OH^-), not what you wrote above.

- Chemistry -
**DrBob222**, Monday, December 13, 2010 at 11:17pm
And my problem is I can't read my calculator. For pH = 9.55, (H^+) = 2.82E-10.

- Chemistry -
**Cliff**, Tuesday, December 14, 2010 at 12:18am
I submitted an incorrect answer to that problem. The correct answer is 0.000 000 000 28 M. I apolgise.

I've been sleep deprived.

- Chemistry -
**DrBob222**, Tuesday, December 14, 2010 at 12:52am
So the answer 2.8E-10 is correct. I should have rounded that last two out of the number and didn't.

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