Question

An aqueous solution contains the following ions: Cl−, F−, HCO−3, Mg2+, and NH+4. Is a precipitate likely to form? If so, give the formula of the precipitate.

A )Mg(HCO3)2
B) MgF2
C) NH4F
D) No precipitate will form

Answer: B) MgF2

Answer 1

MgF2

Step-by-step explanation:

Since the solution is an aqueous solution, then we must recall that only species that are soluble in water will dissolve in it. Chemical substances that are not soluble in water will separate out of the aqueous solution as a precipitate.

Magnesium fluoride is insoluble in water, the fluorides of other group two elements are also markedly less soluble than their corresponding chlorides, bromides and iodides. This lower solubility of alkaline metal fluorides has been related to the extremely high lattice energy of the alkaline metal fluorides. Recall that ionic substances with extremely high lattice energies are often insoluble in water. Hence the answer written above.