Download Chapter 6 Handout

I.
The Mole
A.
Quantity of Particles
1.
The SI unit for the _______________________ is the __________
German : ______________________
Latin: ___________________________
2.
1 mole of a substance = _____________________ items of that
substance.
ex:
1 mole of m & m’s is ___________________ m & m’s
1 mole of water molecules is _______________ water molecules
1 mole of carbon atoms is _________________ atoms of carbon
the mole is a quantity unit like other quantity units, units of
measurement
ex:
1 dozen m & m is 12 m & m
1 gross of m & m’s is 144 m & m’s
3.
This number of items is called ________________ number (N A)
NA = 602, 000, 000, 000, 000, 000, 000, 000
NA = 6.02 x 1023 in scientific notation
4.
Related to chemistry
Avogadro's number = 6.02 x 1023 particles such as _________
_________________________________ and ________________
(ionic compounds)
1 mole of watermelon seeds would fit inside a watermelon slightly
larger than the size of the ___________
1 liter of water contains approximately ________ moles of H2O
which is about 3.3 x 1025 molecules of H2O
Chapter 6
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5.
Calculations
(uses conversion factors)
How many carbon atoms are in 1 mol of carbon?
How many carbon atoms are in 0.1 mol of carbon?
B.
Mole to mole ratios
The number of moles of one substance can be compared to another.
These comparisons can be within a formula or between two formulas
within a balanced equation
1.
Mole ratios within a formula
ex CO2 has 1 mole of C atoms and 2 moles of oxygen atoms
O2 has 2 moles of oxygen atoms
How many O atoms are in 1 mole of O2?
How many Al+3 ions are in 1 mole of Al2O3?
2.
C.
Mole ratios in a balanced equation
mole to mole ratios in a balanced equation will be discussed later
Mass of the mole (molar mass)
Remember the periodic chart and the atomic weights of each of the
elements. Just a reminder, the weights from the chart is for
___________ of the element.
Chapter 6
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1.
For example, 1 atom of hydrogen weighs ____________
(atomic mass units).
What is the mass in grams of 1 atom of Hydrogen?
This is a __________________ of the world.
2.
how to count atoms on a regular basis?
The most usual way to count atoms is by
___________________________________________
If we weigh out ____________ of H, ____________ of Cl and
____________ of Mg, we have the ________________________
of each one of these elements.
This number of atoms is called __________________ number (NA)
and has the value __________________.
Use the atomic weight from the chart and express
it in grams. So one mole of Mg is ___________.
[1 amu is 1.66054 x 10-24 g so 1 g = 6.02 x 1023 amu (inverse)]
Chapter 6
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3.
The mole represents a conversion between grams and atomic
mass units.
_____________________ is the weight in ________ of one mole
The mass in grams of any substance is the same number as its
formula or atomic mass. (the sum of the atomic masses of the
atoms in a formula)
If the atomic mass of a substance is Q amu, then
1:
2:
1 mole of the substance has a mass of Q grams
1 mole of the substance contains 6.02 x 1023 unit particles
What is the mass of 1 mol of C ?
What is the mass of 1 mol of Al2O3 ? (talk later how to get mass of Al2O3)
What is the mass of 0.1 mol of C ?
The Mole
SI unit for amount of substance
1 mole = 6.022 x 1023 particles
1 mole = Formula or atomic mass in grams
Quantity
of
particles
Chapter 6
Mole
Mass
of a
substance
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II
Molar mass, formula weight, molecular weight
A.
_________________________ (MM)
the mass of mole of any substance expressed in grams
element -
1 mole of potassium atoms = _______________
The molar mass of potassium is ________________
compound such as CO2 need to calculate formula weight
B.
_________________________(FW) (Formula mass)
the sum of the atomic masses of the atoms in a formula in ___________
(includes molecules and ionic compounds)
C.
__________________________ (MW) (Molecular mass, subset of FW)
the sum of the atomic masses of the atoms in a molecule in _________
Therefore:
ex:
MW of CO2
ex:
FW of Ca(OH)2
Chapter 6
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III
Problem solving strategies
1.
Identity what you know, write it down
2.
Identity what you want to find out
3.
Identity any intermediate steps and make a plan of the sequence of
conversions
calculate FW etc., unit conversions
4.
If need to calculate something, don’t limit yourself with sig fig from your
calculation, Check the number you have from the question (unless you
have to!!)
5.
Units, carry them through
Solve problems :
Chapter 6
1.
What is the mass in grams of 0.64 mol of Ca(OH)2 ?
2.
How many mol are in 0.64 g of Ca(OH)2
3.
How many oxygen atoms are in 1 mol of Ca(OH)2
4.
How many grams of Oxygen are in 0.25 mol CO2?
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Mole conversion chart
Compound or Atom
Number and Types of Particles
Mass in grams
1 mole carbon
__________________ atoms
____________ g
1 mole oxygen (O)
__________________ atoms
____________ g
1 mole oxygen (O2)
__________________ molecules
____________ g
__________________ atoms
____________ g
0.1 mole carbon
__________________ atoms
____________ g
1 mole aluminum oxide
(Al2O3)
_________________ formula units
____________ g
__________________ Al+3 ions
____________ g
__________________ O-2 ions
____________ g
__________________ ions
Chapter 6
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IV
Mass Percent Composition and Empirical formulas
A.
Definitions
1.
____________________________________
percentages by mass of the elements in a compound.
ex: white solid is 53% K and 47 % O
This means in 100 g, 53 g is K and 47 g is O
2.
______________________________________ - actual number of
atoms of each element
ex: benzene ___________, and acetylene _________
3.
________________________ - simplest formula, simplest whole
number ratios, ratio
ex: both _______
The atom ratios are proportional to the number of moles of
each kind of atom present!!
B.
Determining Mass Percent Composition from Formula
1.
Calculate molar mass
2.
Divide total mass of each element by the molar mass x100
ex: What is the percent composition of H2O?
Chapter 6
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C.
D.
Chapter 6
Determining Mass % Composition from Experimental Data
1.
Calculate mass of compound formed.
2.
Divide mass of each element by total mass x 100
ex:
24.6 g of mercury combine with 8.7 g of chlorine. Calculate %
composition.
Determination of Empirical Formulas Using Percent composition
Determined from experimental data
1.
Assume definite starting amount (100.0 g)
2.
Use molar masses to convert grams of each element to moles:
3.
Divide the number of moles of each element by the smallest of the
quantities
4.
Multiply values from step 3 by the smallest number to make whole
numbers
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Example 1 : Given a compound is composed of 58.81% Ba, 13.73 % S, and
27.46 % O, find the empirical formula
Example 2:
Given grams of a product:
A 6.50 g sample of Chromium was heated in pure oxygen. The compound
produced had a mass of 9.50 g. What is the empirical formula?
Chapter 6
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E.
Molecular formulas
Remember that empirical formulas give a ratio of the elements in the
compound only!
So if have molar mass of a substance and an empirical formula, can
calculate the molecular formula:
Example 1 : The molar mass of benzene is 78.0 g, and the empirical
formula is CH, what is the molecular formula?
Example 2: The molar mass of gasoline is 114.0 g, and the empirical
formula is C4H9, what is the molecular formula?
Chapter 6
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