Chemistry

Chemistry

Problem

When aqueous solutions of lead(II) nitrate and potassium iodide are combined, a yellow solid forms. Which equation best represents the net ionic equation for the reaction? a) 2 K+(aq)+2 I−(aq)→2 KI(s)2\,\mathrm{K}^{+}(aq)+2\,\mathrm{I}^{-}(aq)\rightarrow 2\,\mathrm{KI}(s) b) Pb2+(aq)+2 I−(aq)→PbI2(s)\mathrm{Pb}^{2+}(aq)+2\,\mathrm{I}^{-}(aq)\rightarrow \mathrm{PbI}_{2}(s) c) Pb2+(aq)+2 NO3−(aq)→Pb(NO3)2(s)\mathrm{Pb}^{2+}(aq)+2\,\mathrm{NO}_{3}^{-}(aq)\rightarrow \mathrm{Pb(NO_{3})}_{2}(s) d) Pb(NO3)2(aq)+2 I−(aq)→PbI2(s)+2 NO3−(aq)\mathrm{Pb(NO}_{3})_{2}(aq)+2\,\mathrm{I}^{-}(aq)\rightarrow \mathrm{PbI}_{2}(s)+2\,\mathrm{NO}_{3}^{-}(aq)
Intuitive explanation

This is a precipitation reaction—when two soluble ionic compounds mix, their ions can recombine to form an insoluble solid. The key is to identify which product doesn't dissolve in water, then write only the ions that actually participate in forming that solid, leaving out the "spectator ions" that stay dissolved. Start by writing the full molecular equation, then break it into ions and cancel out anything that doesn't change.

Intuitive explanation

This is a precipitation reaction—when two soluble ionic compounds mix, their ions can recombine to form an insoluble solid. The key is to identify which product doesn't dissolve in water, then write only the ions that actually participate in forming that solid, leaving out the "spectator ions" that stay dissolved. Start by writing the full molecular equation, then break it into ions and cancel out anything that doesn't change.

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