CBSE Class 10 Science 2019 · Paper 31/3/1 · Question 22(b)

Any two of the following: 1. Point the mouth of the boiling tube away from yourself and others, because harmful, pungent gases (${\text{SO}}_2$ and ${\text{SO}}_3$) come out of it. 2. Hold the boiling tube in a slanting (inclined) position while heating it. 3. Hold the boiling tube with a test-tube holder (tongs), never with the bare hand. Other correct precautions, such as using a dry boiling tube, heating it gently and not inhaling the gases directly, also earn credit.