Name:__________________________________________
Define: Mole I mole = ____________________ atoms
1.0 mole of KBr = ________ g
1 mole of C-12 = _________ g
2.0 mol KBr = ________ g
.5 mol KBr = _______ g
Converting Amount to Mass
Problem Hydrogen (molar mass = 2.02 g/mol) is the most common element in the universe, and it is
usually found in the molecular form H2. Determine the mass in grams of 7.55 mol of molecular hydrogen.
SOLUTION
Step 1:
List the given and unknown values.
Given:
amount of hydrogen = 7.55 mol H2
molar mass of hydrogen = 2.02 g/mol H2
Unknown:
mass of hydrogen =  g
Step 2:
Write down the conversion factor that converts moles of molecular hydrogen to grams. The conversion
factor you choose should have what you are trying to find (grams of H 2) in the numerator and what you want to cancel (moles
of H2) in the denominator.
Step 3:
Multiply the amount of hydrogen in moles by the conversion factor you have chosen, and solve.
PRACTICE
1. Uranium (atomic number 92; molar mass = 238.03 g/mol) has the largest molar mass of any element naturally found on
Earth.
What is the mass of 7.50 mol of uranium?
______________________________________________________________________________
2. Ruthenium (atomic number 44) is used as a catalyst and to improve titanium’s resistance to corrosion. It is also one of
the rarest elements in Earth’s crust, making up less than one ten-millionth of the crust’s total mass. Calculate the mass of
37.0 mol of ruthenium.
______________________________________________________________________________
3.Large deposits of manganese (atomic number 25), a metal used to form many different types of alloys, have been found on
the floors of oceans and large lakes. Suppose one of these deposits contains 383 mol of manganese. What is the mass of
the manganese deposit?
Name:__________________________________________
Converting Mass to Amount
After you study each sample problem and solution, work out the practice problems on a separate sheet
of paper. Write your answers in the spaces provided.
PROBLEM
Lithium (molar mass = 6.94 g/mol) is so light that a 0.001 m3 (1 L) volume of it has a mass of only 534 g. What is
the amount in moles represented by this mass of lithium?
SOLUTION
Step 1:
List the given and unknown values.
Given:
mass of lithium = 534 g Li
molar mass of lithium = 6.94 g/mol Li
Unknown: amounts of lithium =  mol
Step 2:
Write down the conversion factor that converts grams to moles.
The conversion factor you choose should have what you are trying to find (moles of Li) in the numerator and what you
want to cancel (grams of Li) in the denominator.
Step 3:
Multiply the mass of lithium in grams by this conversion factor, and solve.
PRACTICE
a. The price of gold (molar mass = 196.97 g/mol) has varied so much over the last 30 years that with $100 you could
buy as much as 2.6 troy ounces (81 g) of gold or as little as 0.13 troy ounces (4.0 g). Calculate the amount in moles
that these two masses of gold represent.
______________________________________________________________________________
b. Aluminum (atomic number 13 =
g/mol) is the most common metal in Earth’s crust. But before the discovery
in 1886 of the process that allowed it to be cheaply extracted from bauxite, aluminum was expensive to process. In
1852, a pound of aluminum cost $545; in 1887 the price was $0.30. At those prices, $100 would buy only 83.2 g of
aluminum in 1852 but 1.51  105 g in 1887. Determine the amount in moles that these two masses of aluminum
represent.
______________________________________________________________________________
c. Osmium (atomic number 76; molar mass =
g/mol) and iridium (atomic number molar mass = 192.22
g/mol) have the highest densities of any elements. A cubic centimeter of either element has a mass of around 22.6 g.
Determine the amount in moles of 22.6 g of each element.
______________________________________________________________________________
Name:__________________________________________
Mixed Practice - do odds
a.
I have 2.5 moles of platinum (atomic # 78). How many atoms is this?
b.
I have 50.0 G of Hg. How many atoms is this?
1.
Tungsten (#74; molar mass =
g/mol), whose high melting point makes it suitable for light bulb filaments
and certain types of steel, is one of the heavier elements; its name even means “heavy stone” in Swedish. What is
the amount in moles contained in a 500.0 g sample of tungsten?
2.
Carbon (atomic #6; molar mass =
g/mol) and lead (#82;molar mass =
g/mol) are the lightest and
heaviest members of their elemental group, respectively. Determine the amount in moles represented by 245 g of
carbon and by 245 g of lead.
3.
Sodium chloride, commonly known as table salt, is the most common type of salt. The chemical formula is NaCl.
(Na =
g/mol + Cl =
g/mol), What is the mass of 29.0 mol of sodium chloride?
4.
Oxygen gas is most often found as O2 (diatomic molecule of element #8; molar mass of O2 = 32.00 g/mol). However,
under certain conditions, a compound called ozone, O3 (molar mass = ________ g/mol) is formed. Ozone, which is
highly reactive and unstable, is formed when O2 is exposed to ultraviolet radiation. Ozone is able to absorb other
ultraviolet radiation, protecting life on Earth’s surface from this harmful radiation.
5.
a.
What is the mass of 17 mol of O2?
b.
What is the mass of 17 mol of O3?
Potassium chloride (molar mass = 74.55 g/mol) is a fairly common salt. Although it is fatal in high doses,
potassium chloride can be safely consumed in small quantities. It is often mixed in small proportions with
sodium chloride to produce “low-sodium” table salt. Determine the amount in moles in 150 g of potassium
chloride.
Name:__________________________________________
6.
Sulfur dioxide (SO2=
g/mol), which is formed when heated sulfur is oxidized, is a pollutant that irritates
lung tissue and makes it more sensitive to dust and other particles inhaled from the outside air. Determine the
amount in moles that would be represented by 27 kg of sulfur dioxide.
7.
After oxygen, silicon is the most common element found in Earth’s crust. Both elements are found in silicon dioxide
(SiO2 ;molar mass = 60.09 g/mol), which is the main component in sand. Suppose you have 893 mol of silicon
dioxide in a sample of sand. What is the mass of the silicon dioxide?
8.
Carbon dioxide (CO2= ___ __ g/mol) is an inert gas that plants need for photosynthesis.
a.
9.
Calculate the mass of 893 mol of carbon dioxide.
Aluminum quickly oxidizes when it is exposed to air, so there is always a thin layer of aluminum oxide (molar
mass = 101.96 g/mol) on any aluminum surface. This oxide layer protects the aluminum from further corrosion.
If the aluminum oxide on several aluminum surfaces has a mass of 79 g, what amount in moles would be
represented by this mass?
10. Sulfuric acid H2SO4(molar mass =
g/mol) is widely used as a corrosive reactant. It is also used in making
fertilizer, detergents, drugs, explosives, and paints, and in the production of other chemicals. The usefulness of
sulfuric acid is so great that it is the most widely produced chemical in the United States. What is the amount in
moles in a sample of sulfuric acid that has a mass of 165 g?
11. Both marble and limestone contain the same mineral, calcite, which consists of the compound calcium carbonate
(molar mass = 100.09 g/mol). What is the mass of a block of calcite if it contains 37 mol of calcium carbonate?