Question

An aqueous solution contains the following ions: Cl-, K+, Mg{2+}, NO3{-}, SO4{2-}. Is a precipitate likely to form? If so, giv ethe formula of the precipitate.

A. MgSO4
B. MgCl2
C. K2SO4
D. No precipitate will form.

Answer 1

D. No precipitate will form.

You must recall the pertinent solubility rules:

1. Salts of Group 1 elements (K⁺) are soluble.
2. Salts containing nitrate ion (NO₃⁻) are soluble.
3. Salts containing chloride ion (Cl⁻) are generally soluble.
4. Most sulfate (SO₄²⁻) salts are soluble.

The only ion not included in the list is Mg²⁺.

However, according to the rules, Mg(NO₃)₂, MgCl₂, and MgSO₄ are soluble.

Thus, there is no precipitate.