Question

Assertion: Molecular weight of oxygen is $$16$$.
Reason: Atomic weight of oxygen is $$16$$.
a) Both Assertion and Reason are correct and reason is the correct explanation of Assertion.
b) Both Assertion and Reason are correct and reason is the not the correct explanation of Assertion.
c) Assertion is correct but Reason is incorrect.
d) Assertion is incorrect but Reason is correct.

Answer 1

Hint: In the modern periodic table, oxygen is present in the ${16}^{th}$ group of p- block family. It has the atomic number $8$. The molar mass of oxygen that we consider was found to be $16$. It is measured in gram per mol.

Complete step by step answer:
Molar mass or molecular mass of an element can be defined as the ratio of mass of chemical compound to the amount of substance present in the sample. It is measured in gram per mol.
For example: the atomic number of oxygen is $8$ and the molar mass of one atom of oxygen considered to be $16gmo{l}^{-1}$.
But oxygen exists in diatomic form, so the molar mass of oxygen molecules will be $32gmo{l}^{-1}$.
Atomic mass of a substance is defined relative to that of mass of carbon with mass $12gmo{l}^{-1}$. It is taken as $12units$.
As the atomic mass of oxygen was considered to be $$16$$, it signifies that when measured the mass of one atom of oxygen, it was found to be sixteen times heavier than one-twelfth of carbon atom in units.
Also as atomic mass of oxygen atom is $16units$ so molar mass of oxygen atom is considered to be $16gmo{l}^{-1}$.
Hence both assertion and reason are found to be correct.
The correct option is (a).

Note:
Oxygen being the first member of the sixteenth group has some different properties. This different behaviour arises due to the small size, high electron density and high electronegativity. It is known as the most electronegative atom in the periodic table after fluorine.