Question

According to Reference Table F, which of these
compounds is the least soluble in water?
(1) K2CO3 (3) Ca3(PO4)2
(2) KC2H3O2 (4) Ca(NO3)2

Answer 1

The answer is (3) Ca3(PO4)2, which is insoluble due to its attraction force between the particles being higher than its attraction force to water molecules.

Answer 2

Answer:- 3) $Ca_3(PO_4)_2$

Explanations:- From solubility rules, all compounds of alkali metals are soluble. K(potassium) is an alkali metal and so potassium carbonate, potassium acetate both are soluble in water.

Also, from the solubility rules, nitrates are soluble, so calcium nitrate is also soluble.

So, the least soluble one will surely be calcium phosphate and also from the solubility rules, phosphates are insoluble(expect of alkali metals and ammonium ion).

Hence, the right answer is 3) $Ca_3(PO_4)_2$ .