When aqueous solutions of are mixed, a precipitate forms.
A) NiBr2 and AgNO3
B) NaI and KBr
C) K2SO4 and CrCl3
D) KOH and Ba(NO3)2
E) Li2CO3 and CsI

A) NiBr₂ and AgNO₃  

Explanation:

We can use the solubility rules to decide which reaction gives the precipitate.

The important ones for this problem are:

The possible products from each reaction are

A) Ni(NO₃)₂ and AgBr; B) NaBr and KI; C) KCl and Cr₂(SO₄)₃

D) KNO₃ and Ba(OH)₂; E) LiI and Cs₂CO₃.

A) Ni(NO₃)₂ and AgBr

Ni(NO₃)₂ — soluble (Rule 2)

     AgBr — insoluble (an exception to Rule 3)

When aqueous solutions of NiBr₂ and AgNO₃ are mixed, a precipitate forms.

B) NaBr and KI

NaBr — soluble (Rule 1)

    KI — soluble (Rule 1)

C) KCl and Cr₂(SO₄)₃

        KCl — soluble (Rule 1)

Cr₂(SO₄)₃ — soluble (Rule 4)

D) KNO₃ and Ba(OH)₂

   KNO₃ — soluble (Rule 1)

Ba(OH)₂ — soluble (Rule 5)

E) LiI and Cs₂CO₃

       LiI — soluble (Rule 1)

Cs₂CO₃ — soluble (Rule 1)

true

hope that

dynamic equilibrium is the answer.