Reef Chemistry Question of the Day #153 Limewater (kalkwasser)

Randy Holmes-Farley

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Reef Chemistry Question of the Day [HASHTAG]#153[/HASHTAG]

Which of the following, when mixed with RO/DI water, will NOT form pure limewater (kalkwasser)? Ignore any gasses that form, which we assume will leave the solution.

A. Calcium hydroxide
B. Calcium hypochlorite
C. Calcium oxide
D. Calcium metal

Note there is only one correct answer. :D

Good luck!






















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143MPCo

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D
 

redfishbluefish

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I shall graciously bow out....but I'll give you the hint that it's not @beaslbob 's go-to answer. (And I think it's Beaslbob who has that go-to answer....if not, I apologize.)
 

JimWelsh

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B, since it's the only one where the substance and water together contain something besides Ca, O, and H.
 

KingBlingTX

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Well, here's what you get from each:

A) Ca(OH)2-> wait this is Kalkwasser!
B) Ca(OCl)2 + H2O --> 2 HOCl + Ca(OH)2
C) CaO + H2O --> Ca(OH)2 = Kalkwasser
D) Ca(s) + 2H2O(l) ——> Ca(OH)2(aq) + H2(g) = Kalkwasser + H2 gas which leaves the solution

So B is the answer.
 

beaslbob

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Well, here's what you get from each:

A) Ca(OH)2-> wait this is Kalkwasser!
B) Ca(OCl)2 + H2O --> 2 HOCl + Ca(OH)2
C) CaO + H2O --> Ca(OH)2 = Kalkwasser
D) Ca(s) + 2H2O(l) ——> Ca(OH)2(aq) + H2(g) = Kalkwasser + H2 gas which leaves the solution

So B is the answer.
dern

You're smart.
 
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Randy Holmes-Farley

Randy Holmes-Farley

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And the answer is...B. Calcium hypochlorite, as KindBling pointed out so well!

People use both CaO and CA(OH)2 (I've used both).

Calcium metal would also work well, but would be hideously expensive and dangerous due to the hydrogen release.

Calcium hypochlorite would likely kill the tank from the bleach produced. :D
 
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