Molar Mass and Molar Mass and Mole Mole

Calculation Calculation ProblemsProblems

Molar MassMolar Mass• You need to calculate molar mass if you

have more than one atom in a problem.• It’s easy… just add the masses together

and multiply time the number of atoms in the molecule (subscript)

• For example: H2O Hydrogen =1 Oxygen =16; There are 2 hydrogens and 1 oxygen so the total is 18g for molar mass…

Give the molar masses of Give the molar masses of the following compounds: the following compounds:

• 1. sodium fluoride NaF

• (1 atom x 23 grams/mole of sodium) + (1 atom x 19 grams/mole of fluorine) = 42 grams/mole of sodium fluoride

• 2. potassium hydroxide KOH

• (1 x 39 grams) + (1 x 1 gram) + (1 x 16 grams) = 56 grams/mole of potassium hydroxide

• 3. copper (I) chloride CuCl

• (1 x 63.5 grams) + (1 x 35.5 grams) = 99 grams/mole of copper (I) chloride

• 4. manganese (IV) oxide MgO2

• (1 x 55 grams) + (2 x 16 grams) = 87 grams/mole of manganese (IV) oxide

• 5. calcium sulfate CaSO4

• (1 x 40 grams) + (1 x 32 grams) + (4 x 16 grams) = 136 grams/mole of calcium sulfate

• 6. magnesium phosphate Mg3(PO4)2)

• (3 x 24 grams) + (2 x 31 grams) + (8 x 16 grams) = 262 grams/mole of magnesium phosphate

How many moles of sodium How many moles of sodium are in 42 g of Na? are in 42 g of Na?

• 1.8 mol Na

How many moles of Oxygen How many moles of Oxygen are in 8.25 g of O? are in 8.25 g of O?

• 0.516 mol O

How much does 2.18 mol of How much does 2.18 mol of Cu weigh? Cu weigh?

• 139 g Cu

What is the mass of 0.28 What is the mass of 0.28 mol of iron? mol of iron?

• 16 g Fe

.    How many atoms are in .    How many atoms are in 7.2 mol of chlorine? 7.2 mol of chlorine?

• 4.3 x 1024 Cl atoms

.    How many atoms are in .    How many atoms are in 36 g of bromine? 36 g of bromine?

• 2.7 x 1023 Br atoms

How many moles are in 1.0 How many moles are in 1.0 x 10x 1099 atoms? atoms?

• 1.7 x 10-15 mol

What is the mass of 1.20 x What is the mass of 1.20 x 10102525 atoms of sulfur? atoms of sulfur?

• 639 g S

How many moles of Carbon How many moles of Carbon monoxide molecules are in 52 g of monoxide molecules are in 52 g of

CO?CO?

• 1.9 mol

.    How many moles of C.    How many moles of C22HH66 are in 124 g? are in 124 g?

• 4.12 mol

.    How many moles of CCl.    How many moles of CCl44 are there in 56 g? are there in 56 g?

• 0.36 mol

How much does 2.50 mol of How much does 2.50 mol of HH22SOSO44 weigh? weigh?

• 245 g

How much does 0.25 mol of How much does 0.25 mol of FeFe22OO33 weigh? weigh?

• 40. g

How many molecules are How many molecules are there in 52 g of CO? there in 52 g of CO?

• 1.1 x 1024 molecules