Question

Write net ionic equations for the oflloiwng molecular eqations. HBr is a strong electrolyte. HBr(aq) + NH3(aq) ----> NH4Br(aq),    2HCl(aq) + Ba(OH)2(aq) ----> 2H2O(l) + BaCl2(aq), Pb(NO3)2(aq) + 2NaBr(aq) ---> PbBr2(s) + 2NaNO3(aq),    MgCO3(s) + H2SO4(aq) ---> MgSO4(aq) + H2O(l) + Co2(g)

Answer 1

We know that while writing complete ionic equation of a molecular equation then, soluble ionic compounds, strong acids, and strong bases written as dissociated ions in the complete ionic equation. Insoluble salts and weak acids are written using the neutral molecular formula since they only dissociate to a very small extent in water. While writing the net ionic equation , sepatator ions (which exists in the both side of the complete ionic equation) are discarded.

Case 1:

molecular equation: HBr(aq) + NH3(aq) ----> NH4Br(aq)

complete ionic equation: H⁺ (aq) + Br^- (aq) + NH₃ (aq) NH₄⁺ (aq) + Br^-(aq)

net ionic equation: H⁺ (aq) + NH₃ (aq) NH₄⁺ (aq) (neglecting the spectator ions)

Case 2:

molecular equation:  2HCl(aq) + Ba(OH)2(aq) ----> 2H2O(l) + BaCl2(aq),

complete ionic equation: 2H⁺ (aq) + 2Cl^- (aq) + Ba²⁺ (aq) + 2OH^- (aq) 2H₂O (l) +  Ba²⁺ (aq) + 2Cl^- (aq)

net ionic equation: 2H⁺ (aq) + 2OH^- (aq) 2H₂O (l) (neglecting the spectator ions)

Case 3:

molecular equation:  Pb(NO₃)₂(aq) + 2NaBr(aq) ---> PbBr₂(s) + 2NaNO₃(aq),

complete ionic equation:

Pb²⁺(aq) + 2NO₃^- (aq) + 2Na²⁺ (aq) + 2Br^- (aq) PbBr₂ (s) +  2Na²⁺ (aq) +2NO₃^- (aq)

net ionic equation: Pb²⁺(aq) + 2Br^- (aq)   PbBr₂ (s) (neglecting the spectator ions)

Case 4:

molecular equation:  MgCO₃(s) + H₂SO₄(aq) ---> MgSO₄(aq) + H₂O(l) + CO₂(g)

complete ionic equation:  

Mg²⁺(aq) + CO₃^2-(aq) + 2H⁺ (aq) + SO₄^2- (aq)   Mg²⁺(aq) + SO₄^2- (aq) + H₂O(l) + CO₂(g)

net ionic equation: CO₃^2-(aq) + 2H⁺ (aq)    H₂O(l) + CO₂(g) (neglecting the spectator ions)