What is the formula for converting grams to moles? And moles to grams?

Note this:

Moles x Grams/Mole = Grams

Grams * Moles/Grams = Moles

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Grams/Mole is the molecular weight (or atomic weight if it's an atom) of the substance.

Moles/Gram is the reciprocal of Grams/Mole.

what is the formula for converting grams to moles? and moles to grams?

To go from grams to moles you divide by the molar mass (atomic mass if its an element, formula mass for ionic compound, etc.)

To go from moles to grams you multiply by the molar mass.