Transcript Slide 1

Practice Test for CHM151 final exam part 2.
The symbols in chemistry get in the way of getting to know elements and compounds.
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H2O is water, true or false? (false)
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The formula for water is H2O, true or false? (true)
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What is the color of Au? (black)
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What is the color of the element represented by Au? (gold or yellow)
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Symbols make elements all look alike. For example (F, Cl, Br, and I) seem like the same size. However, which is
the smallest? (fluorine) The largest? (I)
Ca2+
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Ca and Ca2+ seem like the same size, however, draw them to show their relative sizes. Ca
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O and O2- seem like the same size, however, draw them to show their relative sizes
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CO2 appears to have carbon on the left side and 2 oxygen atoms on the right side. Draw CO 2 using spheres for
carbon and oxygen. Label them.
H
O
O2-
O C O
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Draw the VSEPR structure of H2O.
O
H
Chemistry uses the same symbol for many different things.
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In 3 Liters + 2 Liters, what does the “+” mean? (It means to combine the quantities mathematically.)
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In 2Ag + Cl2  2AgCl, what does the “+” mean? (It means the two are mixed but not necessary combined.)
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In Ag+(aq) + Cl-  AgCl(s), what does the “+” mean by the Ag? (It means Ag has lost an electron giving it a positive 1 charge)
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If the heat of a reaction ΔHrxn = +91kJ, what does the “+” mean? (It means the products of the reaction has gained
91 kilojoules of energy. It is an endothermic reaction.)
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If a drawing shows a “+” in a circle , what is that?
(That is a proton or the nucleus of hydrogen.)
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In “Bring temperature to +25°C.” the “+” means what? (That means 25 degrees above zero.
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In “The change of temperature was +5.5°C.” what does the “+” mean? (The final temperature was 5°C higher.)
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What could “m” mean in chemistry? (milli, meter, or molality (with italicized m).
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What could “M” mean in chemistry? Moles per liter (molarity), Mega, Molar Mass (with italicized M).
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DIMENSIONAL ANALYSIS. Where math classes relied more on solving an equation, chemistry will usually
do dimensional analysis. For example, the equation for distance is d=vt (velocity x time). So this says
multiply velocity times time and you get distance. In chemistry, you don’t think much about the equation but
look at the units. If you see miles per hour and you see hours, you set it up to to get the final units to be a
distance.
55 miles
4 hours =
220 miles
hour
In math, to find t (time), you may solve the equation with algebra to show that t=d/v. So you divide the
distance by the speed. In chemistry, you look at the units. When given a distance of 700 meters per second
and a distance of 2100 meters, you look at the dimensions to tell you how to solve for time. .
1 sec
2100 meters = 3 seconds
700 meters
If the speed was in meters per second but distance was 6 miles, you would do more conversions to get the
answer to have the right unit. You don’t depend on a formula. You let the dimensions tell you what to do.
Dimensional analysis is a series of multiplication problems that often involves multiplying by a rate (e.g.,
1.6km per mile).
1 sec
6 miles 1600 meters
= 13.7 seconds
700 meters
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1 mile
Some problems are best done with a combination of algebra and dimensional analysis.
Concentration x Volume = Concentration x Volume
2 drops of a 4% bleach solution is
diluted to 1 quart. What is its new
concentration in ppm (mg/Liter)?
4g
100 mL
4g
2 drops
100 mL
2 drops Liter
mg
quart
=
?
? mg
=
quart
Liter
Multiply and divide both sides by the units on
the unknown side to isolate unknown (?) value
Look to see what units cancel. If all don’t cancel, add conversion units to cancel all units.
4g
100 mL
2 drops Liter
1 mL
milli 1.057 quarts
mg quart 30 drops 0.001
1 Liter
=
?
Our answer is 2.8. If we wrote
the original unknown
concentration as mg/Liter that
means the answer is 2.8
mg/Liter, which is 2.8 ppm.
MAKE IT REAL. Because chemistry relies heavily on symbols, it is easy to forget what is represented. When
you come across a formula or name for a substance, do a search for images of that substance.
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Know your Internet resources:
– Google (or something similar) for finding Web articles.
– Google (or something similar) for finding images.
– www.wikipedia.com for encyclopedic articles.
– www.dictionary.com for definitions and pronunciations.
– www.webelements.com for information on elements.
– http://www.chemistrycoach.com/tutorial.htm for links to many tutorials.
– http://www.chemtutor.com/ for tutorials.
– www.chemistryland.com your instructor’s website with many PowerPoint presentations.
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Another way to teach yourself about compounds is to build models of them or use chemistry modeling
software. One site that has free computer modeling software is www.acdlabs.com.
BE SKEPTICAL. It doesn’t help to learn a lot of chemistry and then let yourself get duped by bogus products or
stories. To gain awareness of past and present myths and urban legends, visit these sites.
– www.snopes.com
– http://hoaxbusters.ciac.org/
– www.greenfacts.org
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Be more skeptical of information you find. If the site uses the following tactics, be skeptical:
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1. The use of technobabble (technical descriptions that are meaningless and have no basis in real science)
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2. Fantastic claims (When things sound too good to be true, then they probably aren't true. Fantastic health
claims are the most common.)
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3. Something is being sold (when money is at stake, there is more incentive to be deceptive)
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4. Scare tactics (sites that seem to dwell on danger and fear)
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5. Non-balanced discussion (When only one side is presented, then someone is probably biased and the
whole truth isn't told)
GET INSPIRED:
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Chemistry (and science in general) is really amazing. You should always look for ways to be inspired and to
round out your knowledge of current developments.
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Get subscription to science magazines or visit their websites
– Discover
– Popular Science
– Popular Mechanics
– Scientific American
– New Scientist
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Watch DVDs or television programs about science
– Discovery channel: Mythbusters, Alien Planet, I Shouldn’t be Alive, etc.
– Nova series: The Elegant Universe, World in Balance, The Miracle of Life, The Best Mind since
Einstein
– The Learning Channel: Honey We’re Killing the Kids.
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Visit Science Museums, attend conferences, attend presentations and other events.
– Arizona Science Center
– American Chemical Society
– Presenters at ASU, MCC, or elsewhere in the valley.
– Star gazing events.
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Job Shadowing
– Find someone who is in the career that you are aiming for and spend time with them.
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Bring it home
– Get a chemistry kit or testing kits. Look into do it yourself projects (making soap, biodiesel, alcohol,
slime, etc)
– Make your kids “toys” more educational. Microscopes are reasonably priced. Infrared thermometer.
– Visit the science kits online stores.
CHM151final exam part 2 cont’d.
Instructor: Ken Costello
Visuals
Topics
Building Blocks
Forces & Energy
Mathematics
Freezing point
depression is a
achieved by an
antifreeze like
ethylene glycol,
but anything that
dissolves in water
will act as an
antifreeze.
Normally, knowing what
building blocks are present
is important, but for
colligative properties, the
only thing that matters is
what?
When salt is added to ice, it
creates a mixture that is
more random (has more
entropy). This form of
energy gets its energy from
its surroundings by making
it cold. How cold can a
mixture of salt & ice get?
The freezing point depression
constant for water is -1.86C/m. If
292 g (5 moles) of NaCl is added
to 3 L of water, what is new
freezing pt?
A. 6.2°C
A
B. 3.1°C
C. 9.3°C
Fluoride (F-) in
high doses is
lethal, in low
doses it is used to
fight tooth decay.
The mineral in teeth is apatite
with formula: Ca?(PO4)3OH
How many Calciums are needed
to make this compound neutral?
Quantity
Zero degrees Fahrenheit
Five
In chemical
reactions
elements
rearrange
themselves.
Copper metal dipped in a
solution of silver nitrate will
dissolve. The dissolved silver
becomes metallic silver. What
kind of reaction is this?
Acids attack the OH in apatite
turning the OH to H2O. The
apatite is left with +1 charge. How
will water respond?
Prescription fluoride toothpaste
is 0.4% wt/vol fluoride. How
many grams of fluoride in 1 liter
(about 10 tubes)?
Negative end of water will be 4 grams.
Will it kill you if lethal dose is 5
attracted and pull apatite
grams? No.
apart
Write NR next to the ones that
have no reaction:
Fe(s) + Ag+(aq) 
Ag(s) + Al3+(aq)  NR
Au3+(aq) + Ca(s)
Cu(s) + Mg2+(aq)NR
If 127 grams of copper wire
dissolved in AgNO3(aq) to make
copper (I) nitrate, how many
grams of silver precipitated out?
Visuals
Topic
Building Blocks
Forces & Energy
Mathematics
Supernovas are
responsible for
creating the 100+
elements we know
of.
Looking at the atomic weights,
what element needs to fuse with
oxygen to make silicon?
Millions of degrees are needed
for elements to fuse together.
Why?
The remains of a supernova are
neutrons at density of 454 billion
g/cm3. A teaspoon (5 cc) of this
weighs how many lbs.?
A. 17 battleships (5 billion lbs)
Carbon.
To overcome electron
to electron & proton
to proton repulsions
B. 9 locomotives (1 million lbs)
C. 454 billion lbs.
D. 1 million grams.
A
The Periodic Table
of the Elements
organizes
elements in rows
and columns.
If sodium had been the building
block, find an alternative with
similar properties.
One of these: Potassium (K),
Lithium (Li), Rubidium (Rb), or
any from Group 1A.
These seven nonName this compound
metals combine to
P3O5 (2pts)
make poisonous
gases. Knowing which Triphosphorus pentaoxide
gases are lighter or
heavier than air could
save your life.
Which column in the Periodic
Table has elements that pull the
hardest on electrons?
7A
Or 17
Air inside a hot air balloon is a
mixture of nitrogen, oxygen,
carbon dioxide, water vapor, and
carbon monoxide. What force is
causing the hot air balloon to
rise?
Gravity.
Electronegativity measures
attraction to electrons: F=4.0,
Na=0.93, K=0.82, Cl=3.16.
Which has stronger bond, NaF or
KCl?
NaF
To compare densities of gases,
compare molecular weight.
Which is more dense, nitrogen
monoxide or carbon monoxide?
Nitrogen monoxide.
Visuals
Topic
Groups 1A, & 2A
are called alkali
metals & alkali
Earth metals.
The name
“alkali” is Arabic
for the saltwort
plant.
Building Blocks
Forces & Energy
The ashes of the Al Kali plant
Lab students are warned about
contain hydroxides (OH-) of groups adding acids (H+) to bases (OH-).
1A & 1B. These neutralize acids
These neutralize each other, so
(H+) to make what?
what’s the problem?
A lot of heat is produced.
Water
4 moles
(optional) It may boil and
splash.
Water absorbs
Draw a water molecule. Label
heat well, which atoms and show where partial
is why it’s used in charges are..
car radiators.
+
H
Mathematics
Two moles of Ca(OH)2 is mixed
with 3 moles of H2SO4. How many
moles of water is produced?
H
O
How many calories is needed to
What causes water to have a
higher than expected boiling point? raise 53 gallons (200 Liters) of
water in a water heater from 20°C
(room temp) to 70°C?
The + & - ends of
water pull on each
other.
A. 10,000 calories
B. 100,000 calories
C. 10,000,000 calories
C
Living things are
built from 6
elements with a
few metals
needed for
certain proteins.
What are those 6 elements? 6pts
Hydrogen
Carbon
Oxygen
Nitrogen
Sulfur
Phosphorus
In living things, energy from sugar
makes ATP (adenosine
triphosphate) which provides
energy for reactions. How many
phosphate groups are in ATP?
Energy from ribose comes from
this reaction. Balance it.
3
C5H10O5 + 5O2  5CO2 + 5H2O
C5H10O5 + O2  CO2 + H2O
Visuals
Topic
Supernova explosions
spread elements all over
the universe. Gravity
collects elements to
form new stars and solar
systems.
Hoax & Myth Busters.
Building Blocks
Mathematics
Helium is 2nd most abundant
element in universe, yet very
little is on Earth. Why? (2pts)
Would a helium balloon
Abundance is given in %, ppm,
released on surface of the moon or ppb. Write these as fractions.
float or sink? Why? (2 pts)
(3pts)
Being light it is lost to space.
Being inert, it doesn’t bond.
It would fall.
1/100,
Gravity is the reason
1/1,000,000
(optional: there is no air to lift it)
1/1,000,000,000
Gas pressure depends on the
speed of the gas molecules.
How does temperature affect the
speed?
Speed is proportional to
temperature
(or temperature goes up, speed
goes up.)
Some syringes can measure 1
μL of gas. How many atoms of
helium are present if pressure is
1.0x10-4 atm and temp is 0°C.
(R=0.0821)
Carbon & nitrogen are bonded in
the molecule (CN) by sharing 3
electrons each. Nitrogen has
one pair of electrons not
involved. Which would be
attracted to this pair of electrons,
acid [H+} or base [OH-]?
A liter of diet soda has 500 mg
of aspartame. 1/10 of the
aspartame will decompose into
methanol. EPA set daily dose of
0.5 mg per kg body weight for
methanol. I weigh 100 kg. What
is my limit for methanol?
Atoms are too small
to count, so
chemistry resorts to
indirect ways of
counting. I call it
the art of counting
without counting.
Making trillions of molecules of
CO2 is easy: burn coal. Why is
making one molecule hard?
The Internet is full of
hoaxes and myths. Many
relate to chemistry.
Claim: A golfer who had
a habit of chewing on his
golf tee died after playing
4 rounds of golf. He died
from ingesting fungicide
sprayed on the grass by
chewing on the golf tee.
Below is the structure of the
fungicide he died from. If
someone burned this fungicide,
could hydrogen cyanide [HCN]
and hydrochloric acid [HCl] be
products of this burning (assume
hydrogen could come from
moisture in the air)?
Status: TRUE
Forces & Energy
They are too small to see or
handle.
Yes.
50 mg.
If I drink 2 liters of diet soda, do I
go over that limit?
H+
..
…
C N
2.7 trillion atoms of helium
(2.7 x 1012 atoms of helium)
unpaired
Yes.