On heating a mixture of common salt and K₂Cr₂O₇ in equal amount along with concentrated H₂SO₄ in a test tube, a gas is evolved. Formula of the gas evolved and oxidation state of the central metal atom in the gas respectively are:
Q. On heating a mixture of common salt and K₂Cr₂O₇ in equal amount along with concentrated H₂SO₄ in a test tube, a gas is evolved. Formula of the gas evolved and oxidation state of the central metal atom in the gas respectively are:
A. Cr₂O₂Cl₂ and +3
B. Cr₂O₂Cl₂ and +6
C. CrO₂Cl₂ and +6
D. CrO₂Cl₂ and +5
Correct Answer: C

Explanation (Complete Concept Clarity)

When NaCl (common salt) reacts with K₂Cr₂O₇ in presence of concentrated H₂SO₄, chromyl chloride is formed.

This reaction is known as chromyl chloride test.

The gas evolved is:

CrO₂Cl₂

Now calculate oxidation state of chromium in CrO₂Cl₂.

Let oxidation state of Cr = x

Oxygen = −2 each

Chlorine = −1 each

x + 2(−2) + 2(−1) = 0

x − 4 − 2 = 0

x − 6 = 0

x = +6

Therefore, gas evolved is CrO₂Cl₂ and oxidation state of chromium is +6.

Correct Option: C

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