#2xx10^-3*L# of #NaOH# of #0.200*mol*L^-1# concentration is added to #1.00*L# of #1.00*mol*L^-1# #Ca(NO_3)_2(aq)#...will calcium hydroxide precipitate?

1 Answer
anor277
Mar 10, 2017

Calcium hydroxide has a solubility of #1.73*g*L^-1# under standard conditions. This should have been quoted in the question. Calcium hydroxide should not precipitate.

Explanation:

We work out the equivalent quantity of calcium hydroxide, for which we (i) need a stoichiometric equation:

#Ca^(2+) + 2HO^(-) rarr Ca(OH)_2(s) darr#

And (ii) equivalent quantities of the ions in solution:

#"Moles of sodium hydroxide,"# #=# #2.00xx10^-3Lxx0.200*mol*L^-1=4.0xx10^-4*mol#.

And thus when this is added to the bulk solution, we have #[HO^-]# #=# #(4.0xx10^-4*mol)/(1.002*L)=4.0xx10^-4*mol*L^-1#.

Given the stoichiometry, we thus have a solution that is NOMINALLY #2.0xx10^-4*mol*L^-1# with respect to calcium hydroxide.

And this is a mass solubility of,

#74.09*g*mol^-1xx2.0xx10^-4*mol*L^-1=14.8*mg*L^-1# or #"15 ppm"#.

And so calcium hydroxide should NOT precipitate.

Related questions
See all questions in Stoichiometry of Reactions Between Ions in Solutions
Impact of this question
1900 views around the world
You can reuse this answer
Creative Commons License