Question #b64d1

2 Answers
G_Ozdilek
Jul 31, 2017

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.

Jumbotron
Jul 31, 2017

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"

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