Suppose you have asolution that might contain any or all of the followingcations

Question

Suppose you have asolution that might contain any or all of the followingcations: Ni 2+, Ag +, Sr 2+ and Mn 2+. Addition ofHCl solution causes a precipitate to form. After filtering offthe precipitate, H2SO4 solution is added to the resultantsolution and another precipitate forms. This is filtered off, and asolution of NaOH is added to the resulting solution. NOprecipitate is observed.

Which ions are presentin the first precipitate? I believe that the answer here isMn 2+ Ni 2+ and Sr2+ however when I put this into masteringchemistry they say that it is in the correct format. I’m unsure why this is wrong as it is stated that the answershould be reported in ion form.

Which ions are presentin the second precipitate?

Which of the four ionsmust be absent from the original solution?

Can someone help mebreak this problem down to solve it? I really needhelp? J

Explanation / Answer

The ion that presipitate first is Mn 2+ Since Mn 2+ is precipitated as MgCl2 in thepresence of acid HCl ( less acidic ) Mg 2+ + 2HCl ------> MnCl2 + 2H+                                      ppt In the supernantant liquid there is no more Mn 2+ .When we are adding the H2SO4 thenNi 2+ present in the solution will reacts produces ( which requires more acidic nature) H2SO4 + Ni2+ -----> NiSO4 +2H+                                            ppt                                          ppt In the last case Sr 2+ will present in the solution. Sr(NO3)2 + NaOH -----> Sr(OH)2 + NO +NaNO3                                        insolution      ppt Ag + is not present in the original solution                                        insolution      ppt Ag + is not present in the original solution

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