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

FREE Expert Solution

For water, H2O

1 mol H2O = 18.0 g H2O
1 mole H2O = 6.022x1023 H2O molecules

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Problem Details


A single molecule of H2O is 18 atomic mass units. Avogadro’s number of water molecules in a mole of water is shown filling a laboratory-size sample in a beaker; 1 mole of H2O is 18.0 grams.

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.


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

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