Friday, August 25, 2017

inorganic chemistry - What does Pb(NO₃)₂ + KI form?



What does



$\ce{Pb(NO3)2 + KI}$



form?



Answer



This is just a metathesis (double replacement) reaction.



We know that nitrates are soluble, and alkali metals are soluble (at least in these general cases).


Let's ignore balancing for now, and do that last.


$\ce{Pb(NO3)2 + KI -> Pb^{+2} + NO3^- + K+ + I-}$


$\ce{Pb^{+2} + NO3- + K+ + I- -> PbI2 + KNO3}$


But the $\ce{KNO3}$ is also soluble, and would dissociate.


$\ce{Pb^{+2} + NO3- + K+ + I- -> PbI2 + K+ + NO3-}$


Evidently, we can cancel out the spectator ions $\ce{K+}$ and $\ce{NO3-}$ and are left with a net ionic equation (which is easily balanced).


$\ce{Pb^{+2} + 2I- -> PbI2}$


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