Final answer:
When a mixture of NaCl and K₂Cr₂O₇ is gently warmed with conc. H₂SO₄, chromyl chloride is formed and the red vapor produced reacts with NaOH to give a yellow solution of Na₂CrO₄.
Step-by-step explanation:
When a mixture of NaCl and K₂Cr₂O₇ is gently warmed with conc. H₂SO₄, several reactions occur.
One of the correct statements is that the red vapor produced when the mixture is passed into NaOH solution gives a yellow solution of Na₂CrO₄. This is because K₂Cr₂O₇ reacts with conc. H₂SO₄ to form chromyl chloride, CrO₂Cl₂, which is a red vapor. When this vapor reacts with NaOH, it forms Na₂CrO₄, which is a yellow solution. The reaction can be represented as:
K₂Cr₂O₇ + 4NaOH + 6H₂SO₄ → 2CrO₂Cl₂ + 2KHSO₄ + 4H₂O + 4Na₂SO₄
Another correct statement is that chromyl chloride, CrO₂Cl₂, is formed during this process. Chromyl chloride is an orange-red compound that is formed when K₂Cr₂O₇ reacts with conc. H₂SO₄. The formation of chromyl chloride is responsible for the red color of the vapor produced.
In summary, when a mixture of NaCl and K₂Cr₂O₇ is gently warmed with conc. H₂SO₄, the red vapor produced is chromyl chloride, which reacts with NaOH to form a yellow solution of Na₂CrO₄.