Question

The sum of mass of all the atoms in a molecule is known as :

• A. molecular mass
• B. mass number
• C. atomic weight
• D. None of above

Answer 1

The correct option is A molecular mass

The sum of the atomic masses of all the atoms present in a molecule is known as molecular mass. It is therefore a relative mass of a molecule expressed in atomic mass units (u).

For example- molecular mass of carbon dioxide is 44 u and it is calculated as below

The atomic mass of carbon = $12u$ and

The atomic mass of oxygen = $16u$

$\therefore$ molecular mass of $C{O}_2=(1\times atomicmassofC)+(2\times atomicmassofO)$

Molecular mass of $C{O}_2=(1\times 12)+(2\times 16)=44u$

The correct option is A.