Question

Question #b64d1

Answer 1

MW is 18 grams per mol (for water). In 27 grams of water there are `9.03times10^23` molecules of water.

Explanation:

Water has molecular weight of 18 grams per mol (remember that hydrogen atomic weight is 1 and oxygen atomic weight is 16 grams and water formula is `H_2O`).

1 mole of water contains `6.02times10^23` molecules.

If you have 27 grams of water, it means you have `27/18 = 1.5` moles of water.

If you have 1.5 moles of water, it means `1.5times6.02times10^23` water molecules are in it.

When you do the multiplication, you will get

1.5 moles of water contain `9.03times10^23` molecules of water.

Answer 2

`9.03 xx 10^23 "Molecules"`

Explanation:

Recall `-> "no of moles" = "No of Entity"/"Avogadro Constant"`

Also `-> "no of moles" = "mass"/"molar mass"`

Water `-> H_2O`

`"Mass of" color(white)(x) H_2O -> 27g`

`"Molar mass of" color(white)(x) H_2O -> (1 xx 2) + 16 = 2 + 16 = 18gmol^-1`

`:. "no of moles of" color(white)(x) H_2O = (27cancelg)/(18cancelgmol^-1)`

`"no of moles of" color(white)(x) H_2O = 1.5mols`

But `"No of Entity" = "no of moles" xx "Avogadro Constant"`

Hence `"No of Entity (Molecules)" = 1.5 xx 6.02 xx 10^23`

`"No of Entity (Molecules)" = 9.03 xx 10^23 "Molecules"`