Question #b64d1

2 Answers
Jul 31, 2017

Answer:

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.

Jul 31, 2017

Answer:

#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"#