What the mole?!?
You don’t scare me, Chapter 11!
For each question asked:
► Copy
question (These are on the blog if you
aren’t fast enough in class.)
► Determine
asked
► Set
which type of problem is being
up problem (Solving is for homework.)
#1
► How
many molecules are collected in 6.50
moles of CuCl2 ?
#2
► 48.675g
of bismuth represents how many
atoms of bismuth?
#3
► What
is the molar mass of chlorine gas?
 Be careful of the formula!!
#4
Bubba (chemist extraordinaire) wants to
use .450 mol of aluminum sulfide. How
much should be measured onto the
balance?
► Dr.
#5
►A
compound has a molar mass of
110.1g/mol. Its percent composition seems
to indicate an empirical formula of C3H3O.
► Is
that the correct formula for the
compound?
#6
► What
percent of gypsum is actually calcium?
 (gypsum = CaSO4 · 2H2O)
#7
► What
percent of gypsum is actually water?
#8
► How
many moles of iron (III) nitrate are
represented by 43.56mg of the salt?
 (Hey! Is that a milligram?)
#9
► What
is the average mass of 50 atoms of
sulfur?
#10
► Styrene
is 92.25% carbon and 7.75%
hydrogen. What empirical formula does
that indicate?
#11
► The
molar mass of styrene is 104g/mol.
What must be the molecular formula?
 (Yep, use #10 to figure this out.)
#12
► How
many molecules of CO2 are in 44.10g
of carbon dioxide?
#13
► What
percent of anhydrous copper (II)
sulfate is oxygen?
#14
► What
is the empirical formula of a
compound containing:
 10.52g nickel
 4.38g carbon
 5.10g nitrogen
#15
► One
billion molecules of water are in your
hand; how many moles of molecules are
you holding?
Fine’
► So,
how did you do?
► Post
a comment for bonus points! (Shhhh,
it’s our secret!!)
 Valid only for 2/19/10……
#1
► How
many molecules are collected in 6.50
moles of CuCl2 ?
► 6.50mol
►
► 3.91
CuCl2 (6.022 x 1023 molecules)
( 1 mole CuCl2)
x 1024 molecules CuCl2
#2
► 48.675g
of bismuth represents how many
atoms of bismuth?
► 48.675g
►
► 1.403
(6.022 x 1023 atoms Bi)
(208.98038g Bi)
x 1023 atoms of Bi
#3
► What
is the molar mass of chlorine gas?
 Be careful of the formula!! Chlorine is Cl2!!
► 2(35.453g/mol)
= 70.906g/mol Cl2
#4
► Dr.
Bubba (chemist extraordinaire) wants to
use .450 mol of aluminum sulfide. How
much should be measured onto the
balance?
► 0.450mol
►
► 67.6
Al2S3 (150.162g Al2S3)
(1 mol Al2S3)
g Al2S3
#5
►A
compound has a molar mass of
110.1g/mol. Its percent composition seems
to indicate an empirical formula of C3H3O.
► Is that the correct formula for the
compound?
 C3H3O = 55.056g/mol which is only half of the
required 110.1g/mol
► No,
C6H6O2 is the correct molecular formula.
#6
► What
percent of gypsum is actually calcium?
 (gypsum = CaSO4 · 2H2O)
► Ca
x 100
► CaSO4·2H2O
► 40.08/172.18x100
= 23.28% Ca
#7
► What
percent of gypsum is actually water?
► 2H2O
x 100
► CaSO4·2H2O
► 36.030/172.18x100
= 20.926% H2O
#8
► How
many moles of iron (III) nitrate are
represented by 43.56mg of the salt?
 (Hey! Is that a milligram?)
► 43.56mg
►
► 1.801
Fe(NO3)3 (10-3 g)
(1 mole)
(1 mg) (241.859g)
x 10-4 moles Fe(NO3)3
=
#9
► What
► 50
►
is the average mass of 50 atoms of sulfur?
atoms S (32.066 g S)
=
(6.022 x 1023 atoms S)
► 2.662
x 10-21g S (Note: 4 sig figs)
► (Note: the smallest mass unit we saw was the
attogram which is 10-18)
#10
► Styrene
is 92.25% carbon and 7.75%
hydrogen. What empirical formula does
that indicate?
► CH
#11
► The
molar mass of styrene is 104g/mol.
What must be the molecular formula?
 (Yep, use #10 to figure this out.)
► CH
= 13.019g/mol AND 104/13 = 8
► Therefore, styrene is C8H8
#12
► How
many molecules of CO2 are in 44.10g
of carbon dioxide?
► 6.022
► The
x 1023 molecules CO2
mass given happens to be the molar
mass which IS the mass of Avogadro’s
number for CO2 This one of those that if
you recognize that number as its molar
mass, you don’t even have to calculate.
#13
► What
percent of anhydrous copper (II)
sulfate is oxygen?
► 4O/CuSO4
► 40.096%
x 100
oxygen
#14
► What
is the empirical formula of a compound
containing:
 10.52g nickel
 4.38g carbon
 5.10g nitrogen
► Ni(CN)2 nickel
(II) cyanide
► Most of you would have CORRECTLY put NiC2N2
Try to recognize polyatomic ions with metals.
#15
► One
billion molecules of water are in your
hand; how many moles of molecules are
you holding?
►1
►
x 109 molecules H2O (1 mole H2O) =
(6.022 x 1023)
► 1.661
x 10-15 moles H2O, bet you thought it
would be a big number, didn’t you?