Net Ionic equations?

Question

Determine net ionic equations, if any, occuring when aqueous solutions of the following reactants are mixed.
Select "True" or "False" to indicate whether or not the stated reaction (or "no reaction") correctly corresponds to the expected observation in each case.


Sodium phosphate and potassium nitrate; No reaction occurs.

Magnesium chloride and sodium hydroxide; No reaction occurs.

Copper(II) sulfate and ammonium carbonate; No reaction occurs.

Sodium bromide and hydrochloric acid; Na+(aq) + Cl-(aq) --> NaCl(s)

Lead(II) nitrate and sodium chloride; No reaction occurs

Answer 1

Sodium phosphate and potassium nitrate; No reaction occurs.--True

Magnesium chloride and sodium hydroxide; No reaction occurs.--False. MgCl2(aq) + 2NaOH(aq) ==> 2NaCl(aq) + Mg(OH)2(s). The solubility of Mg(OH)2 is very small, only 0.012g/L

Copper(II) sulfate and ammonium carbonate; No reaction occurs.--False. There are two competitive reactions:
CuSO4(aq) + (NH4)2CO3(aq) ==> (NH4)2SO4 + CuCO3(s) << Precipitation
CuSO4(aq) + 4(NH4)2CO3(aq) ==> Cu(NH3)4SO4 + 4(NH4)HCO3 <
Sodium bromide and hydrochloric acid; Na+(aq) + Cl-(aq) --> NaCl(s)--False, even though the acidity of HBr is a little stronger than HCl

Lead(II) nitrate and sodium chloride; No reaction occurs--Kind of true if the reactants are diluted solutions, ---Not true if the reactants are in a high concentration, since PbCl2 solubility in water is less than 10g/L