1. Calculate the number of molecules in 250 mL (1 cup) of water.

Hey there!

The density of water is 1 g/mL.

That means 250 mL of water is 250 grams of water.

Let's find the molar mass:

H: 2 x 1.008 = 2.016

O: 1 x 16 = 16

                    18.016 g/mol

Find the number of moles we have.

250 ÷ 18.016 = 13.88

One mole is 6.022 x 10²³ molecules and we have 13.88 moles.

13.88 x 6.022 x 10²³ = 8.4 x 10²⁴

There are 8.4 x 10²⁴ molecules in 250 mL of water.

Hope this helps!