Mole Conversions

Converting between moles & mass:

• to convert between moles & mass we use molar mass as the conversion factor
• be sure to cancel the appropriate units

Example: How many grams are there in 1.5 mol of O2 ?

• 1.5 mol x (32.0 grams / 1 mol) = 48 grams

Example: How many moles are there in 115 grams of Fe2O3 ?

• 115 grams x (1 mol /  159.6 grams) = 0.721 mol 

Example: A sample of HCl contaims 0.54 mol. How manz grams of HCl 
              is this ?    

• 0.54 mol x (36.5 grams / 1 mol) = 20 grams  

Example: How many moles are present in 2.5 grams sample of Ammonium 
               Phosphate ?  

• NH4 + PO4 3-
• (NH4)3PO4 = 3(14) + 12(1) + 31 + 4(16) = 149
• 2.5 x (1 mol / 149 grams) = 0.017 mol

Example: How many grams are needed to make 2.5 x 10^-3 mol of Cobaltous
              Chloride hexahydrate ?

• Co 2+ Cl -
• CoCl2 x 6 H2O = 58.9 + 2(35.5) + 12(1) + 6(16) = 237.3
• 2.5 x 10^-3 mol x (237.3 grams / 1 mol) = 0.59 grams

Example: A compound is made of P and Cl. It is found to certain 0.200 mol and  

                          has mass of 27.5 grams.

• PxCly
• 27.5 grams / 0.200 mol = 137.5 grams / mol

X	y	Molar Mass
1	2	102
2	1	97.5
2	2	133
1	3	137.5

• PCl3

-Eva