identify the qual 1 cations that are confirmed present in a reference solution b
ID: 491983 • Letter: I
Question
identify the qual 1 cations that are confirmed present in a reference solution by: Experiment 38 Prelab Assignment oratory Qual I. Nat. K+ NH 2+. Ca CU Mg Name Lab Sec. Dale Desk No. 1. the Qual I cation(s) that is (are) confirmed present in a reference solution by a. the formation of a precipitate. Write the formula of the precipitates. the color of a soluble complex ion. write the formula ofthe complex ion. b, c, the characteristic color of a flame test. d, the evolution of a gas. (o) that is (are) confirmed present in a test solution as a result of a Brwnsed aExplanation / Answer
Qualitative analysis of cations
1. Identification by precipitate formation
Addition of dilute HCl gives a Hg2Cl2 as white precipitate : confirms Hg2^2+ present
Hg2^2+ + 2HCl --> Hg2Cl2(white ppt) + 2H+
When we pass H2S gas through the filtrate from above, a black precipitate is formed : confirm Cu2+ present
Cu2+ + S^2- ---> CuS (black ppt)
To the filtrate from above, acidify with HCl, boil and add NH4Cl and (NH4)2CO3 to it. formation of white precipitate confirms Mg2+ or Ca2+
Mg2+ + CO3^2- --> MgCO3(ppt)
Ca2+ + CO3^2- --> CaCO3(ppt)
the rest ions remain soluble
b. For confirmation of Cu2+
dissolve black CuS ppt in HNO3 and add excess NH4OH, formation of blue colored solution confirms formation of complex ion of Cu2+,
Cu2+ + 4NH3 --> [Cu(NH3)4]2+ (blue)
c. Flame tests
Ca2+ : gives brick-red/orange colored flame
Cu2+ : bluish-green colored flame
Mg2+ : intense white flame
K+ : Lilac flame
Na+ : deep yellow flame
NH4+ : faint green
d. From the given ions, we would see evolution of gas, in case of NH4+ ions
NH4+ when heated gives off NH3 gas which forms a white cloud If passed through HCl due to the formation of NH4Cl.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.