Name ___________________________________ Date ____________
Period___
Guided Mole
Directions: Please consult your book (pp. 80-85) to fill in the blanks and answer the questions.
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The mole is the SI _______________ (1) for the amount of substance.
The mole is a ____________________ (2) unit, just like a dozen is.
The number of particles in a mole is known as ________________________________ (3)
number…
_________________________________ (4) number – 6.0221367 x 1023 – is the number of
particles in exactly one _________________ (5) of a pure substance.
o We can use this number as a conversion factor.
For most purposes, Avogadro’s number is rounded to ____________________________ (6).
The mass of one mole of a pure substance is called the _________________ (7) mass of that
substance.
_____________________ (8) mass is usually written in units of ______________________(9).
The molar mass of an element is numerically equal to the _____________ (10) mass of the
element in atomic mass units.
o You can find the molar mass for an element where it is listed on the periodic table.
o The molar mass will be rounded to the hundredth’s place.
A molar mass of an element contains one ___________________ (11) of atoms.
o This means that we can use molar mass as a conversion factor.
Mole conversions
Moles to grams conversion (see sample problem 3-2)
We will use dimensional analysis to convert moles to grams. We can use the molar mass as a
conversion factor. If we use the molar mass as a conversion factor, it is just a ratio that relates
grams and moles.
Take a look at sample problem 3-2: What is the mass in grams of 3.50mol of the element
copper, Cu?
To solve this problem they started with what they were given and used the molar mass as a
conversion factor.
3.50𝑚𝑜𝑙 𝐶𝑢 𝑥
63.55𝑔 𝐶𝑢
Given
(12) Where did they find the 63.55g Cu/mol?
1 𝑚𝑜𝑙 𝐶𝑢
= 222 𝑔 𝐶𝑢
Molar mass
IMPORTANT NOTE: Notice how they labeled their units. They told you what the unit was and
what element that qualified that unit. (for example: mol Cu and g Cu). Make sure that you do
the same when you solve mole problems.
Grams to moles conversion (see sample problem 3-3)
Again, we will use dimensional analysis to convert moles to grams. We can use the molar mass
as a conversion factor. If we use the molar mass as a conversion factor, it is just a ratio that
relates grams and moles.
Take a look at sample problem 3-3: A chemist produced 11.9g of aluminum. How many moles of
aluminum were produced?
To solve this problem they started with what they were given and used the molar mass as a
conversion factor.
11.9𝑔 𝐴𝑙 𝑥
Given
1 𝑚𝑜𝑙 𝐴𝑙
_____________(13) 𝑔 𝐴𝑙
= 0.441 𝑚𝑜𝑙 𝐴𝑙
Molar mass
Atoms to moles conversion (see sample problem 3-4)
We will use dimensional analysis to convert atoms to moles. We can use Avogadro’s number as
a conversion factor. If we us the Avogadro’s number as a conversion factor it is just a ratio that
relates atoms and moles.
Take a look at sample problem 3-4: How many moles of silver, Ag, are in 3.01 x 1023 atoms of
silver?
To solve this problem they started with what they were given and used Avogadro’s number as a
conversion factor.
3.01 𝑥 1023 𝑎𝑡𝑜𝑚𝑠 𝐴𝑔 𝑥
Given
1 𝑚𝑜𝑙 𝐴𝑔
_________________(14) 𝑎𝑡𝑜𝑚𝑠 𝐴𝑔
Avogadro’s number
IMPORTANT NOTE: Notice how they labeled their units.
= 0.500 𝑚𝑜𝑙 𝐴𝑔
Moles to atoms conversion (not in book)
We will use dimensional analysis to convert atoms to moles. We can use Avogadro’s number as
a conversion factor. If we us the Avogadro’s number as a conversion factor it is just a ratio that
relates atoms and moles.
How many moles are there when you have 1.20 x 108 atoms of copper, Cu?
To solve this problem, you start with what you are given and use Avogadro’s number as a
conversion factor.
1.20 𝑥 108 𝑎𝑡𝑜𝑚𝑠 𝐶𝑢 𝑥
1 𝑚𝑜𝑙 𝐶𝑢
_________________(15) 𝑎𝑡𝑜𝑚𝑠 𝐶𝑢
Given
= 1.99 𝑥 10−16 𝑚𝑜𝑙 𝐶𝑢
Avogadro’s number
IMPORTANT NOTE: Notice how the units are labeled.
Atoms to mass conversion (see sample problem 3-5)
We will use dimensional analysis to convert atoms to mass. This is a two-step problem. First we
have to use Avogadro’s number as a conversion factor since it is a ratio that relates atoms and
moles. This first step will give us moles. Next, we have to use the molar mass as a conversion
factor since it is a ratio that relates moles and mass. This next step will give us mass.
Take a look at sample problem 3-5: What is the mass in grams of 1.20 x 108 atoms of copper,
Cu?
To solve this problem, they started with what they are given. First, they used Avogadro’s
number as a conversion factor. Second, they used the molar mass as a conversion factor.
1.20 𝑥 108 𝑎𝑡𝑜𝑚𝑠 𝐶𝑢 𝑥
1 𝑚𝑜𝑙 𝐶𝑢
𝑥
________________(16) 𝑎𝑡𝑜𝑚𝑠 𝐶𝑢
_______________(17) 𝑔 𝐶𝑢
1 𝑚𝑜𝑙 𝐶𝑢
= 1.27 𝑥 10−14 𝑔 𝐶𝑢
Given
Avogadro’s number
Molar mass
VERY IMPORTANT NOTE: There is ABSOLUTELY NO way to convert atoms directly to grams in
one step. If you are looking at the problem and getting confused, consider using two steps. DO
NOT make up conversion factors in order to get your units to cancel. Use conversion factor
(ratio) that you know to cancel your units. Remember molar mass is a ratio of grams to moles;
Avogadro’s number is a ratio of atoms to moles.