How many H2O molecules are in a 9.00-g sample of water? Comparing the mass of 1

Question

How many H2O molecules are in a 9.00-g sample of water?

Comparing the mass of 1 molecule and 1 mol of H2O. Both masses have the same number but different units (atomic mass units and grams). Expressing both masses in grams indicates their huge difference: 1 molecule H2O has a mass of 2.99

Find vo in the circuit in the figure using loop analysis. Comparing the mass of 1 molecule and 1 mol of H2O. Both masses have the same number but different units (atomic mass units and grams). Expressing both masses in grams indicates their huge difference: 1 molecule H2O has a mass of 2.99?10?23 g whereas 1 mol H2O has a mass of 18.0 g.

Explanation / Answer

Number of Moles = Mass of sample/Relative molecular mass

n = mass/mr

Relative molecular mass of water = 18 g/mol

Number of Moles of water = 9/18 = 0.5 mole

There are 6.022 x 10^23 molecules of water in a mole.

Since you have 0.5 mole of substance, you have 0.5 x 6.022 x 10^23 = 3.011 x 10^23 number of water molecules present in that sample

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