Question

solution A solution B Does a precipitate form when A and B are mixed? empirical formula of precipitate potassium sulfide copper(II) nitrate O yes O no sodium hydroxide magnesium bromide O yes O no zinc nitrate iron(II) chloride O yes o no

Answer 1

Solution A	Solution B	Does a precipitate form when A & B are mixed	Empirical formula of precipitate
Potassium Sulfide	Cu(II) nitrate	$\bullet$ Yes O No	CuS
Sodium Hydroxide	Magnesium Bromide	$\bullet$ Yes O No	Mg(OH) 2
Zinc nitrate	Iron (II) chloride	O Yes $\bullet$ No

We can use solubility table to solve this problem.

Consider a reactions.

1) K₂S + Cu(NO₃)₂ $\rightarrow$ CuS + KNO₃

Product KNO₃ is alkali metal nitrate and it is soluble in water.

Product CuS is insoluble in water, hence it precipitates out.

2) 2 NaOH + MgBr ₂$\rightarrow$ Mg(OH) ₂ + 2 NaBr

Product NaBr is water soluble.

Product  Mg(OH) ₂ is insoluble in water, hence it precipitates out.

3) Zn(NO₃) ₂ + FeCl ₂ $\rightarrow$ Fe(NO₃) ₂ + ZnCl ₂

Both products are water soluble. Hence no precipitate forms.

Both products are actually present in the form of ions in the solution, hence it is assumed that there is no reaction. Hence, equation is Zn(NO₃) ₂ + FeCl ₂ $\rightarrow$ No reaction.