Worksheet #13 Using Avogadro’s number and Molar Masses (2p.)
In these problems the compound (or chemical formula) becomes part of the unit:
(e.g. 32.54g NaCl)
1. Calculate the molar mass of each of the following compounds:
AgCl
CaBr2
Li2O
C6H12O6
Fe(NO3)3
Al2 (SO4)3
2. Using the conversion factor [ Molar Mass = 1 Mole] solve the following problems using
dimensional analysis. Keep track of your units!
a) Calculate the mass of 5.634 moles of HCN.
b) Calculate the moles of 257.354g of K2CrO4
c) Calculate the mass of 0.467 moles of CaBr2
d) Calculate the moles of 12.354 grams of C6H12O6
e) Calculate the mass of 8.26 mmoles of KClO4
f) Calculate the moles of 35.7 milligrams of Sr(NO3)2
3. Using Avogadro’s number to convert from molecules or atoms to moles.
A chemical species is either an atom (e.g. K, Ag, S) , an ion (e.g. K+,SO42-, S2-) or a
molecule (e.g. H2O, K2CrO4, Sr(NO3)2, I2). Make sure to learn these vocabulary terms
and the kinds of chemical formulas they indicate.
a) 2.57 x 1011 atoms of silver equals how many moles of silver? [What is the chemical
symbol of silver?]
b) 2.845 x 1012 potassium ions [What is the chemical symbol of the potassium ion?] equals
how many moles of potassium ions?
c) 0.0524 moles of H2O equals how many molecules of water?
d) 347865 atoms of xenon are equal to how many moles of Xe?
e) 3.25 x 1025 atoms of neon gas equals how many moles of neon gas?
f) How many moles of H2SO4 do you have if you there are 1.64 x 1012 molecules of H2SO4?
4. A little Challenge:
a) If there are 8.24 x 1022 molecules of NaCl in a salt shaker, what is the mass of the
salt? First find the number of moles, then convert to grams.
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Worksheet #13 Using Avogadro’s number and Molar Masses (2p.)
Answers.
1. All answers have units of grams/mole
AgCl
143.32g/mol
Li2O
29.88
Fe(NO3)3
241.88
CaBr2 199.88
C6H12O6 180.18
Al2(SO4)3 342.17
All answers to #2, #3 and #4 should have the chemical formula as part of the unit.
2. a) 152.3g HCN
b) 1.3252 mol K2CrO4
c) 93.3 g CaBr2
d) 6.8565 x 102- mol C6H12O6
e) 1.14 g KClO4
f) 1.69 x 10-4 mol Sr(NO3)2
3. a) 4.27 x 10-13 mol Ag
b) 4.73 x 10-12 mol K+
c) 3.15 x 1022 molecules H2O
d) 5.78 x 10-19 mol Xe
e) 54.0 mol Ne
f) 2.72 x 10-12 mol H2SO4
4. a) 8.00 g NaCl
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