Question

An aqueous solution of A gives yellow precipitate with $K_2Cr_2O_4$. A may contain
A.$P{b^{2 + }}$ or $A{g^ + }$ or $B{a^{2 + }}$
B.$P{b^{2 + }}$or $B{a^{2 + }}$
C.$A{g^ + }$ or $B{a^{2 + }}$
D.$P{b^{2 + }}$ or $A{g^ + }$

Answer 1

Hint: The inorganic ions are categorized into different groups for their qualitative analysis. Inorganic salts consist of two parts known as radicals. The positively charged part (cation) is called a basic radical and the negatively charged part of the salt (anion) is called an acidic radical.

Complete step by step answer:
-Qualitative analysis involves the identification of cations and anions which are present in the salt or a mixture of salts. In this type of analysis we try to find out the nature of substance and the identity of the constituents.
-Inorganic qualitative analysis mainly involves the identification of cations and anions with the help of various reagents. The cations are mainly categorized into six different groups. There is systematic analysis.
-Potassium chromate $left( {{K_2}Cr{O_4}} right)$ is used to detect the presence of $P{b^{2 + }}$ and [B{a^{2 + }}]ions.
-In the first group lead is precipitated as lead chloride. On adding a potassium chromate solution, a yellow precipitate of lead chromate is obtained. This confirms the presence of lead ions.
$PbC{l_2}\, + \,{K_2}Cr{O_4} \to PbCr{O_4}\, + \,2KCl$
-The group five cations are precipitated as their carbonates which dissolve in acetic acid due to the formation of corresponding acetates.
-Potassium chromate solution gives a yellow precipitate of barium carbonate when the solution of fifth group precipitate in acetic acid is treated with it.
$BaC{O_3}\, + \,C{H_3}COOH\, \to {(C{H_3}COOH)_2}Ba\, + \,{H_2}O\, + \,C{O_2}$
${(C{H_3}COO)_2}Ba\, + \,{K_2}Cr{O_4}\, \to BaCr{O_4}\, + \,2C{H_3}COOK$
-So we can see that lead and barium ions are detected with the help of potassium chromate solution.
Hence the correct option is B.

Note:
-The structure of potassium chromate is

-Potassium chromate is a water-soluble compound. It appears as a yellow crystalline solid. Its mineral form is called tarapacaite.