how many litres of 0.500M HCL(aq) are needed to react completely with 0.100 mol of Pb(NO3)2, forming a precipitate of PbCl2(s)...please explain

Question

jfraser · Answer

we know that the Cl ions will be reacting with the lead ions, in a 2:1 ratio:$$Pb^{+2} + 2Cl^{-1} \rightarrow PbCl_2(s)$$ we know that you have 0.100mol of lead ions. You have to use twice as many Cl ions (because the balanced reaction says so). So 0.200mol Cl ions are needed. The concentration of HCl is 0.500mol/L This ratio allows us to find$$0.200mol Cl^{-1} * (\frac{1L HCl}{.500mol HCl}) = 0.400L HCl$$