Question

What is active mass?
A. It is a radioactive mass
B. The concentration of a reacting substance
C. Mass which is chemically active
D. Number of molecules which are active

Answer 1

Hint: - For these types of questions we must know the definition of the terms. Here active mass is Active mass is defined as number of grams mol per liter. It is also known as molar concentration or molarity.

Complete answer:
The concentration of a reacting substance is expressed usually in moles per litre.
The concentration of a reacting substance expressed usually in moles per liter also the concentration of the portion of a dissolved electrolyte that is dissociated into ions and hence is capable of carrying.
For the reactant A,
Active Mass =$\dfrac{{Mass\;of\;A\;in\;g}}{{Volume\;of\;solution\;in\;Litre \times Molecular\;Weight\;of\;A\;in\;\dfrac{g}{{mol}}}}$

Hence option B is correct i.e., Active mass is the concentration of a reacting substance.

Note: Generally active mass is a dimensionless quantity but we generally take them with dimensions of molarity, partial pressures etc. Also, in general term we mention them as the effective concentration of a substance