Question

What is a mole ? What is unit of mole ? How many molecules are there in certain mass of substance?

Answer 1

mole is itself a unit. it is a group of 6.022*10²³entities

Answer 2

A convenient amount unit for expressing very large numbers of atoms or molecules is the mole. Experimental measurements have determined the number of entities composing 1 mole of substance to be 6.022 × 1023, a quantity called Avogadro's number. The mass in grams of 1 mole of substance is its molar mass.