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We consider mixing of $\ce{H2SO4(aq)}$ and $\ce{Ca(OH)2}$ in molar ratio 2:1. Molecular equation version: $$\ce{2 H2SO4 + Ca(OH)2 -> Ca(HSO4)2(aq) + 2 H2O}$$ Eventually if $[\ce{Ca^2+}][\ce{SO4^2-}] = [\ce{Ca^2+}] \cdot K_\mathrm{a2} \cdot \frac {[\ce{HSO4-}]}{[\ce{H3O+}]}> K_{\mathrm{sp,}\ce{ CaSO4}}$ ($\mathrm{p}K_\mathrm{a2}=1.99$): $$\ce{Ca(HSO4)2(... 0 I am not sure where your solutions come from but 4.42a isn't correct. The products are calcium sulfate and water, and not, as Poutnik points out, \ce{HSO4-}. So the molecular formula should finish like this: \ce{Ca(OH)2(aq) + H2SO4(aq) -> CaSO4(aq) + 2H2O(l)} Calcium sulfate is actually pretty insoluble so would normally appear as a precipitate but ... -2 The molecular formula:$$\ce{ 2 K3PO4 (aq) + 3Ni(NO3)2 (aq) -> Ni3(PO4)2 (s) + 6KNO3 (aq) }$$The complete ionic formula is:$$ \ce{6K+ (aq) + 2PO4^3- (aq) + 3Ni^2+ (aq) +2NO3- -> Ni3(PO4)2 (s) + 6K^+(aq) + 2NO3^-(aq) }$$The net ionic formula is:$$ \ce{2PO4^3- (aq) + 3Ni^2+ (aq) -> Ni3(PO4)2 (s) }