Question

Analysis of Group 1 Cations

1) Explain what you would do to prove that a solution contained mercury(I) ion.

2) You are given a white solid and told that it is either strontium nitrate or lead(II) nitrate. Explain what you would do to determine the identity of the solid.

3) You are told that an acid is either hydrochloric acid or nitric acid. What simple test could you carry out to tell which acid it is?

4) You are given a solution and asked to determine which group I cations are present in it. Addition of hydrochloric acid results in the formation of a precipitate. The precipitate is washed with hot deionized water. When the filtrate from hot water washing is tested with potassium chromate solution, a precipitate forms. When a solution of ammonia is added to the remaining precipitate from the addition of HCL, it completely dissolves. What do you conclude?

5) A yellow solid is either lead(II) chromate or sodium chromate. What would you do to tell which compound the solid is?

6) Givee an example of a group(IV) cation in the qualitative series.

Answer 1

1) Explain what you would do to prove that a solution contained mercury(I) ion.

First, precipitate in acidic media,

HCl will precipitate with Hg2+2 ion to form

Hg2Cl, then we add Sn2+ ions in order to favour reduction/oxidaiton

Hg2Cl2 + SnCl2 --> 2 Hg(s) + SnCl4

We can confirm this via gravimetric process

2) You are given a white solid and told that it is either strontium nitrate or lead(II) nitrate. Explain what you would do to determine the identity of the solid.

Nitrates are soluble, so

Sr+2 or Pb+2 are present

Both carbonates are not soluble, so add Na2CO3, then via grametric stoichioemtric ratios, determine the mass/moles of base used, the recoevered material, and relate mass to Molar mass of species.

3) You are told that an acid is either hydrochloric acid or nitric acid. What simple test could you carry out to tell which acid it is?

Nitric Acid will Dissolve Solid copper metal, whereas the HCl will NOT

4) You are given a solution and asked to determine which group I cations are present in it. Addition of hydrochloric acid results in the formation of a precipitate. The precipitate is washed with hot deionized water. When the filtrate from hot water washing is tested with potassium chromate solution, a precipitate forms. When a solution of ammonia is added to the remaining precipitate from the addition of HCL, it completely dissolves. What do you conclude

Ag+ is present, since it forms soluble complex Ag(NH4)2+

This is most likely Lead, since it will preicptiate with dichromate and will not dissolve when addition of base

5) A yellow solid is either lead(II) chromate or sodium chromate. What would you do to tell which compound the solid is?

Most sodium compunds are soluble, if it is soluble, then this is sodium chromate

6) Givee an example of a group(IV) cation in the qualitative series.

Ca2+, Ba2+, Mg2+, K+ , Na+ , NH4 +