Question

Be sure to answer all parts. How many total moles of ions are released when the following sample dissolves completely in water? Enter your answer in scientific notation. 2.11 × 10−4 g of Ca(NO3)2: ___× 10__ mol

Answer 1

gram molecular weight of Ca(NO3)2    = 40+ 14*2 + 16*6   = 164g/mole

no of moles of Ca(NO3)2   = W/G.M.Wt

                                           = 2.11*10^-4/164    = 1.286*10^-6 moles of Ca(NO3)2

        Ca(NO3)2 -------------------------> Ca^2+ (aq)   + 2NO3^-

      1.286*10^-6 mole                        1.286*10^-6        2*1.286*10^-6

no of moles of Ca^2+ ions    = 1.286*10^-6 moles

no of moles of NO3^- ions     = 2.572*10^-6 moles

Total no of moles of ions      = 1.286*10^-6 + 2.572*10^-6

                                             = (1.286+2.572)*10^-6

                                             = 3.858*10^-6 moles of ions