[kimi85]

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.

[enahs]

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⁺?

[Borek]

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?

[kimi85]

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

[enahs]

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.

[kimi85]

okay. thank you.