JEE Chemistry 2023 Question with Solution

Given: Two statements about the borax bead test with cupric sulphate in a luminous flame.

Find: Which option correctly evaluates Statement I and Statement II.

In the borax bead test, boric anhydride forms metaborate of the metal, and the bead shows different colours in oxidising and reducing flames.

For copper salt, the solution states:

$$\text{CuSO}_4 + \text{B}_2\text{O}_3 \xrightarrow{\text{Non-luminous flame}} \text{cupric metaborate blue-green}$$

In a reducing flame (luminous flame), the blue-green cupric metaborate does not remain green. It is reduced further, and the bead may become colourless cuprous metaborate or metallic copper, giving a red opaque appearance.

The extracted explanation states that in luminous flame, two reactions may occur and cupric metaborate is reduced. Hence the bead does not become green in luminous flame.

Therefore, Statement I is false.

Also, the green colour is not due to the formation of copper(I) metaborate. The coloured bead is associated with cupric metaborate under non-luminous flame conditions, so Statement II is also false.

Therefore, the correct option is A according to the solution, although the option text corresponding to A says "Both Statement I and Statement II are true" and the final line says "Both Statement I and Statement II are false." This indicates a discrepancy in the solution. Based on the solution's final conclusion about the statements, the defensible choice among the listed options is C.

Given: the solution says "The Correct Option is A", but the worked explanation ends with "Both Statement I and Statement II are false."

Find: The answer consistent with the actual chemical reasoning.

From the chemistry described:

1. Blue-green colour is associated with cupric metaborate in non-luminous flame.
2. In luminous flame, reduction occurs.
3. Therefore the statement that the bead becomes green in luminous flame is false.
4. The statement attributing the green colour to copper(I) metaborate is also false.

So the truth-value pattern is:

$$\text{Statement I = false, Statement II = false}$$

Among the given options, this matches option C.

Thus, the chemically correct answer is C, and the "Option A" label in the solution is inconsistent with the written explanation.