Chemistry
A student reacts copper turnings with cold dilute nitric acid in a test tube. He tests the gas given off with moist red and blue litmus paper. What is the name of the gas that evolved and what is the final colour of the litmus paper?
| Gas | Final colour of the litmus paper | |
|---|---|---|
| 1. | NO | No change in blue and red litmus paper |
| 2. | NO2 | Blue litmus turns red and no change in red litmus |
| 3. | N2 | No change in blue and red litmus paper |
| 4. | N2O | No change in blue and red litmus paper |
Nitric Acid
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Answer
NO, No change in blue and red litmus paper
Reason — Nitric oxide is evolved when cold and dilute HNO3 is added to copper. It is neither acidic nor basic so, it does not change the colour of red or blue litmus paper
3Cu + 8HNO3 ⟶ 3Cu(NO3)2 + 4H2O + 2NO
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