Question

How many molecules are in 240.0 grams of cobalt (II) chloride, CoCl2

Answer 1

The molecules that are in 240 grams of cobalt(ii) chloride COC2 is 1.112 x10^24 molecules

calculation

find the number of moles = mass/molar mass\

molar mass of CoCl2 = 58.9 + 35.5 x2 = 129.9 g/mol

moles= 240g/129.9 g/mol =1.8476 moles

by use of Avogadro's constant

that is 1 mole= 6.02 x10^23 molecules

1.8476 moles=? molecules

by cross multiplication

1.8476 moles x 6.02 x10^23 molecules/ 1moles =1.112 x10^24 molecules

Answer 2

Avagadros number states that 1 mol of any substance is made of 6.022 x 10^23 units

These units could be atoms making up elements or molecules making up compounds

Therefore 1 mol of CoCl2 is Made of 6.022 x 10^23 molecules of CoCl2

Molar mass of CoCl2 is 130 g/mol

Therefore 1 mol of CoCl2 weighs 130 g

So 130 g of CoCl2 contains 6.022 x 10^23 Molecules of CoCl2

Then 240 g of CoCl2 contains - 6.022 x 10^23 / 130 g x 240 g = 1.11 x 10^24 molecules of CoCl2

Answer is 1.11 x 10^24 molecules of CoCl2