Question

 Qualitative Analysis of Metal Cations

 Qualitative analysis can determine the metal cations that are present in a sample based on their solubility characteristics. One such scheme is shown in the flow diagram.

 Some ions that are soluble in all of the test solutions can still be identified based on flame tests. Certain ions impart characteristic color to the flame.

Part A

A solution contains some or all of the ions Cu2+, Al3+, K+, Ca2+, Ba2+, Pb2+, and NH4+. The following tests were performed, in order, on the solution.

Addition of 6 M HCl produced no reaction.

Addition of H2S with 0.2 M HCl produced a black solid.

Addition of (NH4)2S produced a white solid.

Addition of (NH4)2HPO4 in NH3 produced no reaction.

The final supernatant when heated produced a purple flame.

Identify which of these ions were present in the solution, which were absent, and for which ones no conclusions can be drawn.

Drag the appropriate items to their respective bins.

bins are: present. absent. and Inclusive.

options: K⁺ Ba2+ NH₄⁺ Al³⁺ Pb²⁺ Ca²⁺ Cu²⁺

Part B

Select the reagent that will separate the pairs of ions listed.

Answer 1

Concepts and reason

The concept used in this problem is based on qualitative cation analysis.

In the first step, the present, absent and inconclusive cations in the solution are identified. After that, the reagents are matched to the pair of cations that are used to separate them.

Fundamentals

Qualitative cation analysis:

This is an experimental analysis for the identification of cations present in a mixture. This procedure is used to separate and identify the cations by precipitation under a given set of conditions.

The metal ions are classified into five groups and these are separated on the basis of different properties with different reagents.

(A)

The flow diagram of qualitative cation analysis is as follows.

(B)

The reagents that are used to separate the given pair of cations are matched as follows.

Ans: Part A

The present, absent and inconclusive cations are as follows.

Part B

The reagents that are used to separate the given pair of cations are matched as follows.