You are given an unknown sample that when treated with hydrochloric acid forms a precipitate. After decantation, you add boiling water to the solid; some of the solid disappears. You decant the solution and add a few drops of K2CrO4; a yellow solid appears. To the solid left from the addition of boiling water, you add ammonium hydroxide and centrifuge the product. You then decant the liquid and add concentrated nitric acid to the solution until acidic; a white precipitate forms.

Which group 1 cations were present in your unknown?

When we added ammonium hydroxide to the solid remains after addition hot water , AgCl dissolve due to the formation of soluble complex [Ag(NH3)2]+ and Hg2Cl2 gives black precipitate with ammonium hydroxide due to formation of elemental mercury.

Black precipitate is not formed upon addition of amonium hydroxide to the precipitate remains after addition of hot water, so Hg22+ is shown not to be present.

The precepite remains after addition of hot water is dissolved by the addition of ammonium hydroxide, so Ag+ may be present. The presence of Ag+ is not confiremed by K2CrO4 test.

tallinn tallinn · Answer 2 · 2022-04-13T11:49:42+02:00

When The solution is acidic by concentrated Nitric acid forms the white precipitate, which shows the presence of Lead cation group 1

What is Ammonium Hydroxide?

The unknown sample + HCl -----> precipitate forms

The formation of precipitate on treatment with HCl confirms the presence of Group 1

Precipitate + boiling water ------> some solid disappears

If some of the solid disappear in this step, it conducts lead may be present

decant the solution, solid + drops of K2Cr2O7----> no yellow color solid

solid left + ammonium hydroxide + centrifuge ---> no grey / black solid

decant the solution + add con-c Nitric acid -----> White Precipitate forms (lead present)

The above analysis shows the presence of Lead cation in group 1

and absence of Mercury and silver cation of group 1

Group 1 contains three cations lead, silver, and mercury.

According to the scheme of cation analysis on treatment with HCl -----> Precipitate forms

It may contain AgCl, PbCl2 or Hg2Cl2

Precipitate + hot water -----> Precipitate forms ( silver or Mercury may be present)

If ppt dissolves then lead may be attending

additionally on treatment with ammonium hydroxide, centrifugation, and then producing the solution acidic by consolidated Nitric acid forms the white precipitate, which shows the existence of Lead cation.

Find more information about Ammonium Hydroxide here:

https://brainly.com/question/22547992