wikiHow Converting Grams to Moles Practice Problems Remember, to convert grams to moles, you need to divide the number of grams by the molar mass of the substance. 1. If you have 25 grams of calcium carbonate (CaCO3), how many moles is that? 2. How many moles are in 15 grams of nitrogen gas (N2)? 3. A compound has a molar mass of 34 g/mol. If you have 102 grams of the compound, how many moles is that? 4. If you have 18 grams of water (H2O), how many moles is that? 5. How many moles are in 5 grams of sodium hydroxide (NaOH)? 6. If you have 63 grams of ethylene glycol (C2H6O2), how many moles is that? 7. How many moles are in 2.5 grams of carbon dioxide (CO2)? 8. If you have 75 grams of ammonium nitrate (NH4NO3), how many moles is that? 9. How many moles are in 20 grams of aluminum (Al)? 10. If you have 10 grams of methane gas (CH4), how many moles is that? 11. How many moles are in 12 grams of sulfuric acid (H2SO4)? 12. If you have 30 grams of calcium chloride (CaCl2), how many moles is that? 13. How many moles are in 8 grams of glucose (C6H12O6)? 14. If you have 100 grams of sodium chloride (NaCl), how many moles is that? 15. How many moles are in 25 grams of iron (Fe)? 16. If you have 40 grams of ethanol (C2H5OH), how many moles is that? 17. How many moles are in 5 grams of oxygen gas (O2)? 18. If you have 16 grams of methane gas (CH4), how many moles is that? 19. How many moles are in 50 grams of sulfur dioxide (SO2)? 20. If you have 90 grams of potassium permanganate (KMnO4), how many moles is that? Page