Which has the largest number of molecules?

a)54g of N₂O₅

b)36g of H₂O

c)25g of CO₂

d)46g of C₂H₅OH

Mass of N2O5 = 54g

Moles of N2O5 = 54g / 108 g mole−1 = 0.5 moles

Mass of H2O = 36 g

Moles of H2O = 36g / 18 g mole−1 = 2 moles

Mass of CO2 = 25 g

Moles of CO2 = 25g / 44 g mole−1 = 0.568 moles

Mass of C2H5OH = 46 g

Moles of C2H5OH = 46g / 46 g mole−1 = 1 moles

Greater the number of moles of a compound greater will be the number of molecules. Hence 36 g of water with 2 moles (greater the number of moles when compared to others in the list) has the greater number of molecules.