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Topic: Is calcium hydroxide soluble in NaOH ?  (Read 25269 times)

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Offline Kate

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Is calcium hydroxide soluble in NaOH ?
« on: November 22, 2007, 02:38:48 PM »
Hi. :)
My question is: is Ca(OH)2 soluble in NaOH ? Thanks.

Offline Borek

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #1 on: November 22, 2007, 03:11:55 PM »
How do you think?
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Offline Kate

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #2 on: November 22, 2007, 03:15:15 PM »
How ? Sorry, but I'm not getting the question.

Anyway, if it is, then is this the right equation:
Ca(OH)2 + 2OH- -> [Ca(OH)4]2-   ?

Offline Borek

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #3 on: November 22, 2007, 05:39:01 PM »
Oops, what, not how. CC of Polish way of asking this question >:(

The only Ca/OH- complex I am aware of is CaOH+. Calcium is not amphoteric, so Ca(OH)42- doesn't exist. Or rather - even if it exist, stability constant is too low for the complex to be of any importance. Thing that can't be neglected when mixing Ca(OH)2 and NaOH is the common ion effect.
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Offline Kate

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #4 on: November 22, 2007, 06:05:00 PM »
Thing that can't be neglected when mixing Ca(OH)2 and NaOH is the common ion effect.

I was thinking about that too, but Be(OH)2 is soluble in NaOH and there's formation of [Be(OH)4]2-. How is this explained ? I'm not exactly an expert on Chemistry, as you can probably see, but does this difference have anything to do with the fact that Be(OH)2 isn't soluble in water, while Ca(OH)2 is ? And so, in the case of Be(OH)2, the common ion effect "problem" doesn't exist ?

Offline Borek

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #5 on: November 22, 2007, 06:43:38 PM »
Be is less metalic then Ca.
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Offline Kate

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #6 on: November 23, 2007, 10:49:59 AM »
And how does that explain that Be(OH)2 is soluble in NaOH, while Ca(OH)2 isn't ?

Offline Borek

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #7 on: November 23, 2007, 03:01:47 PM »
The more metallic element, the less it is inclined to get amphoteric. In general amphoteric elements lay on the diagonal (upper left - bottom right) of the periodic table. For example Al, Sn, Bi fit this description. Be to some extent too. Ca is too far from the diagonal.

Note - it is all hand waving, but close enough to reality ;)
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Offline Kate

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #8 on: November 26, 2007, 09:54:07 AM »
Thanks.

Offline clarkexxx

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #9 on: November 26, 2007, 02:20:07 PM »
I have been dealing with similar problem but I would postulate the question this way: Is Ca(OH)2 soluble in NaOH solution? and how much?. I know, from my experience, that if you mix 0.1M NaOH aqueous solution of with saturated aqueous solution of Ca(OH)2 then something immediately precipitates from the solution.  My guess is that it is Ca(OH)2 but has anyone any sophisticated explanation for this ?

Offline Borek

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #10 on: November 26, 2007, 04:24:17 PM »
IMHO solubility product is sophisticated enough :)
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Offline AWK

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #11 on: November 27, 2007, 01:29:18 AM »
I have been dealing with similar problem but I would postulate the question this way: Is Ca(OH)2 soluble in NaOH solution? and how much?. I know, from my experience, that if you mix 0.1M NaOH aqueous solution of with saturated aqueous solution of Ca(OH)2 then something immediately precipitates from the solution.  My guess is that it is Ca(OH)2 but has anyone any sophisticated explanation for this ?
This is a common ion effect. Calculations needs Ksp (solubility product)
AWK

Offline Kate

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #12 on: November 27, 2007, 06:52:11 PM »
Let's imagine that I mix SbCl3 with KI. The reaction is given by the following equation: Sb3+ + 6I- -> [SbI6]3-

What happens (if anything) when excess of I- ions are added to the solution containing [SbI6]3- ?

Offline Borek

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Re: Is calcium hydroxide soluble in NaOH ?
« Reply #13 on: November 28, 2007, 03:53:22 AM »
Most likely nothing. But to be sure you should check stability constants, chemistry of such mixtures can be pretty complicated.
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