Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: kimi85 on September 01, 2007, 10:46:56 PM
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Calculate [H3O+] and pH in saturated Ba(OH)2 (aq), which contains 3.9 g Ba(OH)2 . 8 H2O per 100 ml solution.
What I did I first find the molarity then multiplied it to two. The I calculated the H+ using the ionization constant of water. But my answer is wrong. I calculated pH from pOH and my answer is wrong too. What is wrong with my computation?
The correct answer is 4 x 10-3 M H3O+ and pH is 12.4.
Thank you.
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The correct answer is 4 x 10-3 M H3O+ and pH is 12.4.
That is impossible.
You either typed it wrong or read the answer wrong.
What would be a pH of a solution with 4x10-3 M H3O+?
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Show your numbers, approach (through pOH) seems correct. The only obvious mistake I can think off is molar mass of hydrated hydroxide - have you forgot water, or not?
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I'm sorry for the error. It should be 4 x 10-13 M H3O+
I also included the molecular weight of the hydrate but I'm still wrong
Here's what I did:
(3.9/315.46)/0.1 L = 0.1236 x 2 = 0.24725 pOH = 0.60686 pH = 14-pOH = 13.39
3O+:
1 x 10-14/0.24724 = 4 x 10-14
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The answer you are giving as the correct answer for the conditions you are giving are for 0.39 g of Ba(OH)2.
However 3.6 g is much closer to the real solubility value.
It looks like when working the solution they forgot to divide by 0.1L.
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okay. thank you. :)