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Topic: LiOH solubility, am I wrong?  (Read 3226 times)

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Offline BTEW13

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LiOH solubility, am I wrong?
« on: July 01, 2014, 02:09:26 PM »
I'm new to this forum but had a question about an exam I took recently in my undergraduate chemistry class. The exam contained a list of compounds and I was required to label whether each was soluble, insoluble, or slightly soluble. My professor marked that I got two wrong and I still think I was right.

One was Lithium Hydroxide (LiOH) and the other was Sodium Chromate (Na2CrO4). I marked that each was soluble and my professor claims that each is only slightly soluble. According to the chart in my text book that states the solubility rules for ionic compounds in water, these two should both be soluble.

Does anyone here have any input as to whether or not I'm right and if not, why?

btw, I did use the search function before I made a new topic.

Thanks in advance

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Re: LiOH solubility, am I wrong?
« Reply #1 on: July 01, 2014, 03:00:29 PM »
Solubility of sodium chromate: around 25% w/w (more precisely, 47 g of Na2CrO4ยท10H2O per 100 g of water). Well soluble if you ask me.

Solubility of lithium hydroxide: definitely lower, around 11% w/w (12.8 g of LiOH per 100 g of water). Still, that's 5 mol/liter, well soluble if you ask me (although it has much lower solubility than other alkali metals hydroxides).

Unless you were told what it is supposed to mean in the context of the course "slightly soluble" is a useless term, as it is not well defined and ambiguous. For me both substances are well soluble, even if LiOH definitely differs from its analogues.
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Offline Babcock_Hall

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Re: LiOH solubility, am I wrong?
« Reply #2 on: July 01, 2014, 04:51:56 PM »
I recently made a stock solution of lithium hydroxide at 2 M.  Old LiOH (s) picks up carbon dioxide from the atmosphere, and Li2CO3 is not very soluble.

Offline Hunter2

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Re: LiOH solubility, am I wrong?
« Reply #3 on: July 02, 2014, 12:01:12 PM »
The soloubilty of LiOH is the lowest in the row of the alcali elements.  LiOH < NaOH < KOH> RbOH< CsOH.

Sodiumdichromate: I would say good solubilty in comparison of potassium dichromate.

Offline Krakenshark

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Re: LiOH solubility, am I wrong?
« Reply #4 on: March 24, 2020, 03:00:28 PM »
i'm afraid your wrong. if something is soluble that means it will completely dissolves in water. slightly soluble means it will only dissolves a bit in water. when a question ask if something is soluble or not, they want to know if 100 g of the substance will completely dissolve in water.

Offline chenbeier

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Re: LiOH solubility, am I wrong?
« Reply #5 on: March 24, 2020, 03:39:46 PM »
Soloubility of LiOH is 12,8 g / 100g H2O

Calculate yourself how  much water you need for 100 g LiOH.

Offline mjc123

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Re: LiOH solubility, am I wrong?
« Reply #6 on: March 24, 2020, 04:45:13 PM »
Quote
i'm afraid your wrong. if something is soluble that means it will completely dissolves in water. slightly soluble means it will only dissolves a bit in water. when a question ask if something is soluble or not, they want to know if 100 g of the substance will completely dissolve in water.
That's not a meaningful definition. 100g of anything will dissolve in water, if you have enough water.

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