Observing the changes, in which of the following would you say a chemical reaction may be occurring? (i) Heating iodine changes the colour from bluish black to purple. (ii) Mixing ammonia and hydrogen chloride gases gives fumes containing a white powdery substance. (iii) Mixing an acid and a base solution raises the temperature. (iv) Mixing ferrous sulphide and hydrochloric acid gives off a gas with a rotten egg smell.

Observing the changes, in which of the following would you say a chemi

1.	Observing the changes, in which of the following would you say a chemical reaction may be occurring? (i) Heating iodine changes the colour from bluish black to purple. (ii) Mixing ammonia and hydrogen chloride gases gives fumes containing a white powdery substance. (iii) Mixing an acid and a base solution raises the temperature. (iv) Mixing ferrous sulphide and hydrochloric acid gives off a gas with a rotten egg smell.
Answer» Observing the changes, in which of the following would you say a chemical reaction may be occurring? (i) Heating iodine changes the colour from bluish black to purple. (ii) Mixing ammonia and hydrogen chloride gases gives fumes containing a white powdery substance. (iii) Mixing an acid and a base solution raises the temperature. (iv) Mixing ferrous sulphide and hydrochloric acid gives off a gas with a rotten egg smell.