Question

complete the table below by deciding whether a precipitate forms when aqueous solu formula in the last column. solution a solution b does a precipitate form when a and b are mixed? empirical formula of precipitate zinc nitrate ammonium sulfide yes no sodium acetate barium bromide yes no sodium hydroxide magnesium bromide yes no

Explanation:

Step1: Write the chemical formulas

Zinc nitrate: \(Zn(NO_3)_2\), ammonium sulfide: \((NH_4)_2S\). When they react, using double - displacement reaction (cation - exchange), the products are \(ZnS\) and \(NH_4NO_3\). According to solubility rules, sulfides of transition metals (zinc is a transition metal) are insoluble. So \(ZnS\) is the precipitate.

Step2: Second pair

Sodium acetate: \(NaC_2H_3O_2\), barium bromide: \(BaBr_2\). The possible products are \(NaBr\) and \(Ba(C_2H_3O_2)_2\). All acetates and bromides (except for \(Ag^+\), \(Pb^{2 +}\), \(Hg_2^{2+}\)) are soluble. So no precipitate forms.

Step3: Third pair

Sodium hydroxide: \(NaOH\), magnesium bromide: \(MgBr_2\). Using double - displacement reaction, the products are \(Mg(OH)_2\) and \(NaBr\). According to solubility rules, hydroxides of group 2 metals (magnesium is in group 2, but it should be noted that for hydroxides, \(NaOH\) is soluble, \(Mg(OH)_2\) is insoluble as hydroxides of \(Mg^{2+}\) (except for hydroxides of group 1 metals and \(Ba(OH)_2\), \(Sr(OH)_2\) which are soluble to some extent) are insoluble). So \(Mg(OH)_2\) is the precipitate.

Answer:

solution A	solution B	Does a precipitate form when A and B are mixed?	empirical formula of precipitate
sodium acetate	barium bromide	no
sodium hydroxide	magnesium bromide	yes	\(Mg(OH)_2\)