Solubility

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barlow_2
Posts: 6
Joined: Mon Jun 01, 2020 5:23 pm

Solubility

Post by barlow_2 » Thu Jul 23, 2020 7:29 pm

I am watching the solubility video and have confused myself about something. In the quiz it says that hydroxides are insoluble (Ex: Na(OH)2). However, we know that Na(OH)2 is a strong base and will dissociate completely. How is it possible that it dissociates completely but is insoluble? Would really appreciate any help! I can't wrap my head around this simple concept!
NS_Tutor_Nancy
Posts: 47
Joined: Wed May 27, 2020 7:25 pm

Re: Solubility

Post by NS_Tutor_Nancy » Thu Jul 23, 2020 8:50 pm

Hey!

You are right, it wouldn't make sense for something to be a strong base but also be insoluble. When it comes to solubility rules, the rule on hydroxides is a little more complicated than just saying all hydroxides are insoluble, there are some exceptions! Hydroxides salts of group I elements (like NaOH) and ammonium (NH4OH) are soluble. Hydroxide salts of group II elements (like CaOH2) are slightly soluble. The rest are insoluble.

I hope this helps!
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