The average molecular weight of the air which has $21 \%$ of $O_2$ and $79 \%$ of $N_2$, is

$1 \ u \ (amu)$ is equal to

One atomic mass unit $(amu)$ is equal to:

Which symbol replaced the unit of atomic mass,$amu$?

In order to prepare one litre of a $1 \ N$ (normal) solution of $KMnO_4$,how many grams of $KMnO_4$ are required if the solution is used in an acidic medium for oxidation?

The unit of atomic mass,$amu$ is replaced by $u$,here $u$ stands for