Question

Which amongst the following observations does not indicate that a chemical reaction has occurred?

• A. Formation of a precipitate
• B. Production of gas
• C. Evolution of heat and light
• D. Change in total mass of substance

Answer 1

The correct option is D Change in total mass of substance

According to law of conservation of mass, during a chemical reaction, there is no change in the total mass of the substance.

However, the indicators of chemical reactions include:
$\bullet$ change in temperature
$\bullet$ change in colour
$\bullet$ formation of precipitate
$\bullet$ evolution of gases
$\bullet$ change in odour