Question

What’s the formula mass of NaCl?

(a) 23 u

(b) 35.5 u

(c) 58 u

(d) 58.5 u

This question was addressed to me in a job interview.

The above asked question is from Atomic and Molecular Masses in section Chemistry Basic Concepts of Chemistry – Class 11

Answer 1

Correct choice is (d) 58.5 u

Explanation: As Cl in NaCl can’t exist in the solid state, we can only calculate it’s formula mass. the individual mass of sodium is 23 u, whereas that of chlorine is 35.5 u. Together formula mass f Sodium chloride is the sum of individual masses, 23 + 35.5 = 58.5 u.