9.2 Chemists use relative masses to count atoms and molecules How to measure a specific number of atoms and molecules? By relative masses or molar mass(摩尔质量). 2H2 2 HO 2 moles 1 mole 2 moles Which is Which is Which is 4 grams 32 grams 36 grams Which is Which is which is 12.04×1023 molecules 6.02×1023 molecules 12.04×1023 molecules9.2 Chemists use relative masses to count atoms and molecules How to measure a specific number of atoms and molecules? By relative masses or molar mass (摩尔质量). 2H2 + O2 = H2O 2 moles 1 mole 2 moles Which is Which is which is 4 grams 32 grams 36 grams Which is Which is which is 12.04×1023molecules 6.02×1023molecules 12.04×1023molecules