Transcript Packet 7 - Kentucky Community and Technical College System

Packet 8
Solutions
“Divide, and conquer.”
Phillip of Macedon
“Nothing in the world is as soft and yielding as water. Yet for
dissolving the hard and inflexible, nothing can surpass it.”
Tao Te Ching, ca. 500 B.C.
last updated: 7/17/2015
CHE 140 Packet 8 - 1
Concept Area I: Terminology
colloid
complete ionic
equation
concentrated
concentration
dilute
dilution
dissolve /
dissociate
dissolving /
dissociating
electrolytes
Henry’s law
hydration
insoluble /
immiscible
mass percent
Molarity, M
molecular /
complete formula
equation
net ionic equation
nonelectrolytes
precipitate
saturated
solubility
soluble / miscible
solute
solution
solvent
strong
supersaturated
suspension
unsaturated
weak
CHE 140 Packet 8 - 2
Concept Area II: Solutions and Electrolytes
a. You should understand the difference between a solute, solvent,
solution, colloid and suspension.
b. You need to have an understanding of solubility and be able to
classify a solution as saturated, unsaturated or supersaturated.
c. You should be able to explain why certain compounds do and do not
form solutions based on the principle of “like dissolves like”.
d. You need to understand what effect temperature and pressure have
on solutions.
e. You should understand the term electrolyte and know what ions are
formed when one dissolves in water.
f. You should be able to classify a compound as a strong, weak or a
nonelectrolyte.
g. You are not responsible for equivalents, osmosis or freezing
point/boiling point changes.
CHE 140 Packet 8 - 3
Water, water everywhere…
• Most of the solutions we form are water based. Why?
• Well, ¾ of the Earth is covered by water.
• And, 70-80% of us is water.
• Because water is so abundant it is very useful to use as a solvent.
The fact that so many ionic and molecular chemicals are soluble
in it makes it even more useful.
• Many chemists are even trying to do all their experiments
in water since it is so much more environmentally
friendly, green chemistry.
• Since water is so common as a solvent, we have
a special name for solutions that use water as
the solvent, aqueous. Remember that it can be
abbreviated “aq” when labeling a species in a
chemical reaction.
CHE 140 Packet 8 - 4
Solution Composition
solute: the substance
dissolved in a solvent to
form a solution; it is
normally the component of a
solution present in the lesser
amount.
solvent: the dissolving
medium of a
solution; it is normally
the component of a
solution present in the
greater amount.
solution: a mixture of
substances that has a
uniform composition; a
homogeneous mixture –
thus, everything is in the
same phase.
Timberlake page 297 (also see figure 8.1)
CHE 140 Packet 8 - 5
Different kinds of Solutions
• A solution is a homogeneous mixture of two or more
substances in a single phase: solid, liquid, gas. The
solute cannot be filtered out or removed with a
semipermeable membrane.
Rubies are a solution of red chromium
compounds with transparent aluminum
oxide. Fillings are also a metal
solution as are all metal alloys!
When you blow
up a balloon, you
are filling it with
a gaseous solution
of O2, CO2 and
other gases.
Also see table 8.1 on page 298 of Timberlake.
Mixing sugar into
water makes a
sugar water
solution once the
sugar dissolves.
CHE 140 Packet 8 - 6
Suspensions & Colloids (discussed in section 8.6)
suspension: a mixture of
two or more substances
where the solute will
eventually settle out or can
be filtered out or separated
by a semipermeable
membrane.
colloid: a state of matter
intermediate between a
solution and a suspension, in
which solute particles are
large enough to scatter light
but too small to settle out.
A filter will not separate,
but a semipermeable
membrane will.
In this picture, notice that the laser
light is not scattered by the true
NaCl solution on the left, but it is
scattered by the colloidal gelatin
mixture on the right.
CHE 140 Packet 8 - 7
Solubility
• Solubility is how well a solute dissolves in a
solvent to form a solution.
• The more soluble or miscible something is,
the _______
easier it is to make a solution.
• Sometimes something is so soluble we could
put large amounts in. Others are so insoluble
that maybe one molecule or formula unit
dissolves in a swimming pool full of solvent.
• What determines a compound’s solubility in a
particular solvent? The intermolecular forces
between the solute and the solvent!
CHE 140 Packet 8 - 8
Solutions and Solubility
• unsaturated solution: the solvent is not holding
all of the solute that it can at that temperature,
more could dissolve if added.
• saturated solution: the solvent is holding the
maximum amount of solute it can at that
temperature; the solution is at equilibrium with
the same amount of solute coming out of
solution as is being dissolved.
• supersaturated solution: the solvent is holding
more than the maximum amount of solute it
normally can at that temperature – very unstable,
the least little thing will cause the excess solute
to come out of solution.
CHE 140 Packet 8 - 9
Saturated vs. Unsaturated
Let’s say that under these
conditions 200 g of this
solid can dissolve.
For the beaker on the left,
we have only added 150 g.
Thus, the solution is
unsaturated.
For the beaker on the right,
let’s say we added 250 g.
Since the solution can only
hold a maximum of 200 g,
the remaining 50 g sits on
the bottom. This solution
is saturated. Recall that
we’re at equilibrium
between solid dissolving
and precipitating.
Timberlake page 306
CHE 140 Packet 8 - 10
http://www.youtube.com/watch?v=jVhPZg3dxIg
Saturated vs. Unsaturated vs. Supersaturated
In the beaker below we have a
supersaturated solution of
sodium acetate being poured out
onto a few seed crystals. The
excess solute comes out readily.
Notice that the unsaturated
solution and the supersaturated
solution look the same
macroscopically. Only the
saturated solution can be
differentiated by appearance
only. How can we tell the
unsaturated and
supersaturated solutions apart?
Left images from Timberlake page 306
CHE 140 Packet 8 - 11
Intermolecular Forces Review
• Okay, we learned all about intermolecular forces in
chapter 5.
• So, what forces apply when something interacts only
with itself?
• intermolecular forces
• induced dipole-induced dipole
• dipole-dipole
• H-bonding
• bonds
• ion-ion
• (covalent)
These forces can also be found in solutions.
• Now, what intermolecular forces did we leave out?
• dipole-induced dipole
• ion-dipole
These are only found in solutions.
CHE 140 Packet 8 - 12
LIKE DISSOLVES LIKE!
• Okay, so we already learned the intermolecular
forces if we only have one compound present.
• Let’s apply intermolecular forces to solutions!
• If we mix two different chemical species, what
determines whether they are soluble in each other
or not?
Like dissolve like - if both chemicals have
the same intermolecular forces, they
will be soluble in each other.
• Sometimes dissimilar compounds can dissolve:
dipole-induced dipole and ion-dipole. But,
compounds always prefer to dissolve in “like”
compounds.
CHE 140 Packet 8 - 13
LIKE DISSOLVES LIKE!
Water is a _________
molecule that can ___________________
polar
H-bond
with itself. I2 is a nonpolar
_________molecule that has
__________________________
induced
dipole-induced dipole with itself. CCl4 is a
_________
__________________________
dipole-induced dipole
nonpolar molecule that has induced
with itself.
Now, I2 can dissolve in water using ______________________,
dipole-induced dipole
but if given the choice between polar water and nonpolar
CCl4, I2 will choose CCl4 as these pictures show. Does this
make sense? Why?
CHE 140 Packet 8 - 14
Note of caution….
• In our text on page 301, they tell us
that CH2Cl2 is nonpolar.
• However, we know that it is polar!
• So, why do they say it is nonpolar
and why does it not mix with water
when like should dissolve like?
It really is polar, but is in only slightly
polar, so our book decided to call it
nonpolar. As for the layers, it only dissolves
a little bit in water (about 15g/1L) and the
rest sinks to the bottom. Since most doesn’t
dissolve, we say they are insoluble.
right image Timberlake page 301
CHE 140 Packet 11 - 15
Like Dissolves Like Quiz
Determine if the following will form solutions or not. Why?
1.
O2 in H2O
Miscible because polar H2O induces a dipole in O2.
dipole-induced dipole
2.
CH3(CH2)6CH3 in H2O
Not miscible because polar H2O is unable to induce
a dipole in the large nonpolar octane.
3.
NaCl in H2O
NaCl is soluble in polar solvent like water.
ion-dipole
4.
CH3Cl in H2O
Like dissolves like! Both are polar.
dipole-dipole
5.
CH3Cl in CH3(CH2)6CH3
6.
CH3COOH in H2O
Not miscible because polar CH3Cl is unable to induce a dipole in
the large nonpolar octane.
Like dissolves like! Both are polar and capable of H-bonding!
H-bonding: special case of dipole-dipole
Whole slide (with answers) shown on notes page.
CHE 140 Packet 8 - 16
Solubility of Solids versus Temperature
• The solubility of solids
usually increases in liquid
solvents as the temperature
increases.
• Why?
Because as the temperature
increases, the solvent molecules
have ______
more kinetic energy.
Thus, the solvent particles move
_______
faster and are able to disrupt
the solute particle-to-particle
attractions ______.
more
Timberlake page 307
CHE 140 Packet 8 - 17
Solubility of Gases versus Temperature
• Gases follow the reverse trend of solids. As
temperature increases, gases are less soluble in
liquid solvents. Why?
Because as we increase the temperature, the
kinetic energy for all particles _________.
increase As
the gas particles move _________________,
faster and faster
______
more of them escape from the solvent into
the atmosphere.
• Final question, what is in the bubbles of a boiling
liquid after it has been boiling for several minutes?
It would be the gaseous form of the
liquid! All of the dissolved gases have
already left!
CHE 140 Packet 8 - 18
Solubility of Gases versus Pressure
(Henry’s Law)
• As pressure increases, gases are more soluble in
liquid solvents.
• Why?
Because as we increase the
pressure, the gas molecules
need more
______ energy to
escape into the atmosphere.
At those higher pressures,
_______
fewer gas molecules have
enough energy to escape, so
______
more are left in solution.
Timberlake page 309
CHE 140 Packet 8 - 19
Aqueous Solutions of Ionic
versus Molecular Compounds
Although many solutes are soluble/miscible in water, there
are two different ways they can dissolve in it.
1) They can separate into ions. What are some examples
What are some examples? of ionic compounds?
NaCl, HCl, NaOH, H2SO4, CH3COOH, Ca2NO3,
NH4OH, etcetera
2) The solute can be attracted to the solvent. Hey, that
sounds like _______________________!
intermolecular forces
What are some examples (no ionic compounds!)?
CH3CH2OH, sugar, Cl2, O2, etcetera
Once again we have special terms; compounds of type 1 are
called electrolytes and type 2 are called nonelectrolytes.
CHE 140 Packet 8 - 20
What ions do we get?
• Remember how we learned to put together
ions using charge balance?
• Pb2+ and S2– would form? PbS
• Ca2+ and F– would form? CaF2
• Al3+ and O2– would form? Al2O3
• Let’s now reverse that and rip them apart!
What ions would these soluble compounds
form in water?
• NaOH
• Pb(NO3)2
• Al2(SO4)3
 Na+ + OH–
 Pb2+ + 2 NO3–
2 Al3+ + 3 SO42–
CHE 140 Packet 8 - 21
How does water dissolve something?
• First, remember that the shape of water makes it polar.
Thus, one side of it partially
negative and the other side
partially positive.
• Ions are either positive
or negative, right?
• So, the “negative” side
of water surrounds
cations, and the
“positive” side of water
surrounds the anions.
see figure 8.2 in Timberlake page 300, too
CHE 140 Packet 8 - 22
Ionic Compounds
Let’s look at an example of an
ionic compound, potassium
permanganate,
dissolving/dissociating in
water:
So, the ions formed in the
aqueous solution would be?
K+(aq) + MnO4–(aq)
And that makes the formula?
KMnO4
Ionic compounds are also
electrolytes, let’s examine what
this means…
CHE 140 Packet 8 - 23
Electrolytes & Nonelectrolytes
• Electrolytes when put into an aqueous
solution form what? ions
• Do nonelectrolytes form them? Nooo!
• Pure water does not conduct electricity.
Water with only nonelectrolytes in it does
not conduct electricity. Water with
electrolytes present does conduct electricity.
Hint: what do electrolytes do that pure
water and nonelectrolytes don’t?
For electricity to be conducted, ions need to be present so
that the charged electrons can move through the
solution. Pure water and nonelectrolytes have only
molecules; therefore, no electrons can move through.
Why?
CHE 140 Packet 8 - 24
Here’s a picture that
represents what
happens to the ions
when electricity is put
through a solution of
ions.
The movement of the ions
allows for the electrons
to flow.
If there weren’t ions,
electrons would be
unable to move through
the solution.
CHE 140 Packet 8 - 25
Notice that these pictures represent what is happening at the
submicroscopic level. You can see the water molecules interacting
with the ions or molecules present. In your book (page 301) you can
see how the ions interact with the electrodes.
similar images on Timberlake page 302
CHE 140 Packet 8 - 26
These pictures
are also trying
to represent
what is
happening at
the microscopic
level, but the
water
molecules have
been omitted
for clarity.
CHE 140 Packet 8 - 27
Electrolytes, Weak Electrolytes and Nonelectrolytes
Okay, so we now know the difference between electrolytes and
nonelectrolytes. But, what makes one electrolyte strong and
another weak?!?!
• Strong electrolytes dissociate (break apart) or ionize
completely , and thus, are good .
conductors of electricity. Experimental proof:
.
light bulb lit up very brightly
• Weak electrolytes dissociate or ionize
, and thus, are poor .
a little
conductors of electricity. Experimental proof:
.
light bulb lit up dimly
• Nonelectrolytes dissociate or ionize
, and thus, are not
.
none
conductors of electricity. Experimental proof:
light bulb did not light up
.
Note: strong and weak do not refer to concentration in this context!
CHE 140 Packet 8 - 28
Strong vs. Weak
• Acids, bases and electrolytes can be
classified as either strong or weak.
• What determines if strong or weak?
The number of ions and molecules in
solution.
The more an electrolyte breaks apart
into ions in solution, the stronger
it is.
The less an electrolyte breaks apart
into ions in solution, the weaker it is.
If no ions in solution, then it’s a
nonelectrolyte.
CHE 140 Packet 8 - 29
Strong Electrolytes – ions in solutionElectrolytes Handout
1) All soluble salts (even if only slightly soluble).
.
2) Strong bases – Group
1A and 2A hydroxides
3) Strong acids – HCl,
HBr, HI, HNO3, HClO4, H2SO4
.
Weak Electrolytes –
Memorize!
ions & molecules in solution
Electrolyte
Classes!
1) None
2) Weak bases – NH3, etc.
3) Weak acids – CH3CO2H, etc.
Nonelectrolytes – no ions, just molecules in solution
1) Insoluble salts
4) All other compounds not already covered.
CHE 140 Packet 8 - 30
Concept Area III: Writing Different
Types of Chemical Reactions
a. You need to be able to write the molecular
(complete formula equation), complete
ionic equation and net ionic equation for
chemical reactions.
b. You need to be able to read a solubility
table to predict the identity of a precipitate
that forms as a result of a double
replacement chemical reaction.
CHE 140 Packet 11 - 31
Solubility Rules
Timberlake page 309
CHE 140 Packet 8 - 32
Solubility Chart you may see on exam:
SOLUBLE COMPOUNDS
Almost all salts of Na+, K+, NH4+
Salts of nitrate, NO3–
chlorate, ClO3–
perchlorate, ClO4–
acetate, CH3CO2–
EXCEPTIONS
Almost all salts of Cl–, Br–, I–
Halides of Ag+, Hg22+, Pb2+
Compounds containg F–
Fluorides of Mg2+, Ca2+, Sr2+, Ba2+, Pb2+
Salts of sulfate, SO42–
Sulfates of Mg2+, Ca2+, Sr2+, Ba2+, Pb2+
INSOLUBLE COMPOUNDS
EXCEPTIONS
All salts of carbonate, CO32–
phosphate, PO43–
oxalate, C2O42–
Salts of NH4+ and the alkali metal cations
chromate, CrO42–
Most metal sulfides, S2–
Most metal hydroxides and oxides
Ba(OH)2 is soluble
CHE 140 Packet 11 - 33
How to predict precipitates when solutions
of two ionic compounds are mixed
 Step 1 Write the reactants as they actually
exist before any reaction occurs. Remember
that when a salt dissolves, its ions separate.
 Step 2 Consider the various solids that could
form. To do this, simply exchange the
anions of the added salts. Ah, a double
replacement reaction!
 Step 3 Use the solubility rules to decide
whether a solid forms and, if so, to predict
the identity of the solid.
CHE 140 Packet 8 - 34
Molecular or Complete Formula Equations
2 AgNO3(aq) + CaCl2(aq) →2 AgCl(s)+ Ca(NO3)2(aq)
This is a complete formula equation; it’s not
really a molecular equation because we have
ions and not molecules. However, most
chemists will call this a molecular equation.
Note that we have written everything together
as formulas. We’ve even shown what state the
chemicals are in to make it complete.
CHE 140 Packet 8 - 35
2 AgNO3(aq) + CaCl2(aq) → 2 AgCl(s)+ Ca(NO3)2(aq)
Complete Ionic Equations
(note our text calls these “ionic equations”)
2 Ag+ + 2 NO3– + Ca2+ + 2 Cl– → 2 AgCl + Ca2+ + 2 NO3–
Note that here we wrote everything how it
actually exists in the solution. The soluble
salts ionize and are written as ions. The
insoluble salts don’t ionize and are written
with the ions together. You may still put in the
states; we didn’t have room here.
So in a complete ionic reaction, separate all the
ionic compounds that are “aq” and leave
together all the “s”, “ℓ” and “g”!
Could we write one of these for a molecular
equation? Sure, why not? However, since no ions it will
look the same as the molecular equation!
CHE 140 Packet 8 - 36
2 Ag+ + 2 NO3– + Ca2+ + 2 Cl– → 2 AgCl + Ca2+ + 2 NO3–
Net Ionic Equations
2 Ag+ + 2 Cl– → 2 AgCl
Note here we only wrote those species that
were different in products and reactants.
The rest did not participate, they “watched.”
So, they are called spectator ions.
CHE 140 Packet 8 - 37
Your Turn!
Be sure to revisit the Oxidation Numbers &
Writing Different Kinds of Equations Chapter 5
Handout
Write all three kinds of equations for the following:
molecular/complete formula
1. Al(NO3)3(aq) + 3 NaOH(aq) → Al(OH)3(s) + 3 NaNO3(aq)
complete ionic
Al3+ + 3 NO3– + 3 Na+ + 3 OH– → Al(OH)3 + 3 Na+ + 3 NO3–
net ionic
Al3+ + 3 OH– → Al(OH)3
2. When aqueous solutions of copper(II) nitrate and potassium
carbonate are mixed, a precipitate forms.
molecular/complete formula
Cu(NO3)2(aq) + K2CO3(aq) → CuCO3(s) + 2 KNO3(aq)
complete ionic
Cu2+ + 2 NO3– + 2 K+ + CO32– → CuCO3 + 2 K+ + 2 NO3–
net ionic
Cu2+ + CO32– → CuCO3
CHE 140 Packet 8 - 38
Concept Area IV: Molarity and Stoichiometry
a. You are not responsible for percent
concentration (however still responsible for
percent composition that we learned
previously).
b. You should be able to define Molarity, moles
of solute per one liter of solution.
c. You should be able to interconvert between
grams, moles, Molarity and volume for the
reactants or products in a balanced chemical
equation.
d. You should be able to calculate dilutions.
CHE 140 Packet 8 - 39
The Mole Refresher
• Remember, 1 mole is the amount of
substance that contains as many particles
(atoms, molecules, whatever) as there are in
12.0 g of 12C.
• And remember that there is Avogadro’s
number of particles in a mole of any
substance.
• What is Avogadro’s number?
6.022×1023
CHE 140 Packet 8 - 40
Molarity Handout
Solution Concentration: Molarity
To indicate how much solute we have in a solution,
Molarity is commonly used. It is abbreviated with
a capital “M”. It is defined:
mols of solute
M
1 L of solution
“Molarity” is usually
used as a noun. If an
adjective is needed to
mean the same thing,
chemists use the term “Molar”.
I will usually always capitalize “Molarity” and
“Molar” since the symbol is a capital “M”.
similar images on Timberlake on page 315
CHE 140 Packet 8 - 41
A “road map” between grams, moles,
number of particles and Molarity!
mass of element or
compound
MM
number of
particles
A’s #
Avogadro’s number
6.022×1023
molar mass(es)
from periodic table
moles of element
or compound
V
Volume
Molarity
CHE 170 Packet 4 - 42
mols of solute
M
1 L of solution
Note that it is per liter of solution and not per liter of
solvent. Just because we know how much solvent we
added doesn’t mean we know how much solution we
have!
This picture shows very
clearly that a one liter
solution (in the
volumetric flask) is
quite different than
one liter of solvent
(the water in the
volumetric flask and
the graduated
cylinder).
CHE 140 Packet 8 - 43
Here we have a 1L
of a 1M sucrose
solution. This
means that we
have 1 mole of
sucrose (the
solute). This also
means we have
342 grams of
sucrose. And, it
also means we
have 6.02×1023
sucrose
molecules. Just
because we know
all this does not
mean we have to
use all of it in a
calculation!
CHE 140 Packet 8 - 44
Let’s do an example!
What concentration, in Molarity, is the solution shown
above? The pictures says we took 0.435 g of
potassium permanganate and made a 250.00 milliliter
solution.
0.435g KMnO4
1 mol KMnO4
5 mol KMnO4

 1.1010
250.00mL solution 158.04g KMnO4
mL solution
Are we done? Are we in units of M?
No! Need mol/L!
1.1010-5 molKMnO4 1000mL

 0.0110M KMnO4
1 mL solution
1L
CHE 140 Packet 8 - 45
Your turn to try one!
Calculate the mass of Na2SO4 needed to
prepare 0.500 L of a 0.150 M solution.
0.150 mol Na 2SO 4
 0.500 L Na 2SO 4  0.0750 mol Na 2SO 4
1 L Na 2SO 4
142.04 g Na 2SO 4
0.0750 mol Na 2SO 4 
 10.7 g Na 2SO 4
1 mol Na 2SO 4
CHE 140 Packet 11 - 46
Some other problems for home practice:
Answers
“Muriatic acid” is sold in many hardware stores for cleaning
5.99 M
bricks and tile. What is the Molarity of this solution if 125
mL of this solution contain 27.3 grams of HCl?
2. Silver chloride is only marginally soluble in water; only
0.00019 grams of AgCl dissolves in 100 mL of water.
1.3×10–5 M
Assuming that only 100 mL of solution is made; calculate
the Molarity of this solution.
3. You are told that you have a cholesterol level of 160 mg per
4.14×10–3 mol/L dL blood. If the molecular mass of cholesterol is 386.67
grams/mol, what is your cholesterol level in mol/L?
4. How many moles of NH3 are in 2 liters of a 14.8 M
29.6 mol
solution?
1.
See notes page for these problems worked out.
CHE 140 Packet 8 - 47
Dilute vs.
Concentrated
• Solutions can be dilute or concentrated.
• dilute: very few ions/molecules in solution.
• concentrated: a lot of ions/molecules in solution.
Note these definitions are pretty much consistent
with how we use outside of science.
• The concentration of a solution is dependent only
on how much solute is present in the solvent.
• 0.1 M NaCl is a dilute salt solution
• 5.0 M NaCl is a concentrated solution
Timberlake on page 319
CHE 140 Packet 8 - 48
Strong vs. Weak – Review!
• Acids, bases and electrolytes can be
classified as either strong or weak.
• What determines if strong or weak?
The number of ions and molecules in
solution.
The more an electrolyte breaks apart
into ions in solution, the stronger
it is.
The less an electrolyte breaks apart
into ions in solution, the weaker it is.
If no ions in solution, then it’s a
nonelectrolyte.
CHE 140 Packet 8 - 49
Strong
vs.
Weak
versus
Concentrated
vs.
Dilute
Science uses these terms differently than non-science uses. Do
you know how to use scientifically? Label the following
strong/weak and concentrated/dilute appropriately.
1.
2.
3.
4.
5.
6.
7.
1.
1.
0.001 M NaCl (aq) 2.
2.
12.0 M HCl (aq)
3.
6.0 M CH3COOH (aq)3.
4.
0.05 M NaOH (aq)
4.
8.0 M RbOH (aq)
5.
0.0001 M Na2SO4(aq) 5.
6.
0.10 M NH3 (aq)
6.
7.
7.
strong electrolyte
dilute solution
strong acid
concentrated solution
weak acid
concentrated solution
strong base
dilute solution
strong base
concentrated solution
strong electrolyte
dilute solution
weak base
dilute solution CHE 140 Packet 8 - 50
Dilutions: M1V1=M2V2
How do we make 500 mL of a 0.00100 M solution of
K2Cr2O7 if we only have a 0.100 M solution and of the
same and water to make it from?
M1V1  M 2 V2
(0.100 M)(V1 )  (0.00100M)(500mL)
(0.00100M)(500mL)
V1 
(0.100 M)
V1  5.00 mL
Ah, so we used 5.00 mL of the 0.100 M solution and diluted
it to 500 mL (with about 495 mL of water) to make our
solution!
Note: This formula is only to be used with dilutions! If the
mixed chemicals react, this formula cannot be used!
CHE 140 Packet 8 - 51
How to do a dilution in the lab:
similar images on page 320 of Timberlake
CHE 140 Packet 8 - 52
Now you try a dilution calculation!
What is the Molarity of a solution formed
when 15.0 mL of 5.00 M HCl is diluted to
50.00 mL?
M1V1  M 2 V2
(5.00 M)(15.00mL)  M 2 (50.00mL)
M 2  1.50M
And now back to stoichiometry!
CHE 140 Packet 11 - 53
Expanded General Plan for Stoichiometric Calculations
Step 1) write a balanced chemical reaction.
Step 2) write
Mass down what we know
Mass
product
Step 3)reactant
write down what we want to know
Step
4)
solve
the
problem
using
our
new
and
molar mass(es)
molar mass(es)
MM
MM
improved
roadmap!
from periodic table
from periodic table
Moles
reactant
Volume V
Molarity
reactant
mol:mol ratio
use stoichiometric
factors from balanced
chemical equation
Moles
product
V
Volume
Molarity
product
CHE 140 Packet 8 - 54
Stoichiometry meets Molarity practice!
1. If we react 1.0 L of 0.44 M HCl with 30 g NaOH
26 g
how many grams of NaCl can we make?
(answer of 44 g means forgot to take limiting reagent into account!)
2. What is the Molarity of sulfuric acid if it takes 20.03
0.0668 M mL of 0.100 M NaOH to neutralize 15.00 mL of the
sulfuric acid?
3. If we react 3.25 g of zinc with excess 5.00 M
0.100 g
hydrochloric acid at STP, how much hydrogen gas
1.11 L
will be produced (in grams and liters)? Note, the
other product formed is ZnCl2.
See notes page for these problems worked out.
CHE 140 Packet 8 - 55
The End of Packet 8
Any Questions?
CHE 140 Packet 8 - 56