Question

A green mass is formed in the charcoal cavity test when a colorless salt $\left( X \right)$ is fused with cobalt nitrate. $\left( X \right)$ may contain:
A. Aluminium
B. Copper
C. Barium
D. Zinc

Answer 1

The reaction is a cobalt nitrate charcoal test in which qualitative analysis is done to determine the amount of green mass formed in the reaction. One can draw the reaction by following the given data in the reaction which will give an idea about which salt is formed in the reaction that is green in color.

Complete step by step answer:
-First of all we will learn about the qualitative analysis reaction which is a method used in analytical chemistry that deals with the determination of the presence of elemental composition in an inorganic salt. The main purpose of performing this method is to detect ions in the salt aqueous solution.
-Now we will learn about the charcoal cavity test where is a part of the preliminary qualitative inorganic analysis.
-The colorless salt $\left( X \right)$ may contain zinc let's analyze the following reaction,
$ZnS{O_4} + N{a_2}C{O_3}\xrightarrow{{}}ZnC{o_3} + N{a_2}S{O_4}$
$ZnC{O_3}\xrightarrow{{}}ZnO + C{O_2}$
$2Co{(N{O_3})_2}\xrightarrow{{}}2CoO + 4N{O_2} + {O_2}$
$CoO + ZnO\xrightarrow{{}}CoZn{O_2}$
Now, the product formed is $CoZn{O_2}$ which is a zinc cobalt oxide complex that is green in color.
Hence, the green color of the product shows that the $\left( X \right)$ contain zinc which shows option D as a correct choice.

Note: The cobalt nitrate test is an elongated process of the charcoal cavity test. The charcoal cavity test is conducted by mixing the given salt which in this case is $\left( X \right)$ with sodium carbonate and then heating the mixture on the block of charcoal by using the tool of the blowpipe in reducing flame. The given inorganic salt then gets converted to its respective oxides having characteristic colors.