Question

What is gram molecule? And gram equivalent?

Answer 1

These are obsolete terms.

Explanation:

Gram molecule is defined as the number of grams of a substance that is the same as the relative molecular mass of that substance.

A mole is defined as `6.02...*10^23` molecules, atoms, ions or whatever.

In practice, these mean the same, though officially there is a difference, somewhere far behind the decimal point.

(something like the `L=` liter and `dm^3=` cubic decimeter)

A gram equivalent is the number of grams that is equivalent to one gram of hydrogen, i.e. that can react with, or replace one gram of hydrogen. This is not the same as the above!
E.g. the gram equivalent for oxygen is `~~8g`, while a mole of oxygen atoms would be `~~16g` and a mole of oxygen molecules (`O_2`) will be `~~32g`