How many molecules in a glass of water?

Question

A glass holds 250 millilitres of water. Water has molecular mass 18 (grams per mole), and a mole contains about 6 × 10 to the 23 molecules. 1. How many water molecules are in the glass? 2. The oceans hold about 1.3 × 10 to the 21 litres of water. How many glassfuls is that? Compare with your answer to part 1, and draw the famous conclusion about drinking a glass of water that was once drunk by Julius Caesar.

Accepted Answer

About 8 × 10 to the 24 molecules per glass. The oceans hold about 5 × 10 to the 21 glasses. So there are more molecules in one glass than there are glasses in the sea, by a factor of over a thousand. Molecules in the glass. 250 mL of water is 250 grams, which is 250 / 18, about 14 moles. Times Avogadro's number: 14 × 6 × 10 to the 23, about 8 × 10 to the 24 molecules. Glasses in the ocean. 1.3 × 10 to the 21 litres divided by 0.25 litres per glass gives about 5 × 10 to the 21 glasses. The conclusion. Suppose the water Caesar drank in one glass, two thousand years ago, has by now been thorough…

How many molecules in a glass of water?

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