Hourly Exam # 1 Dunnivant
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There are 100 points. The exam will be graded on a percentage
basis.
The honor statement must
be signed in order for your exam to be graded.
Closed book, closed Internet,
closed notes, closed neighbor!
I have neither given nor
received aid on this exam.
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________________________
AvogadroÕs number = 6.022 x
1023 items/mol
amu = 1.6605 x 10-24
g/amu
electron charge = 1.602 x 10-19
C
mass of neutron = 1.6749 x 10-24
g
mass of electron = 9.1094 x
10-28 g
mass of proton = 1.6726 x 10-24
g
NOTES:
-Show all work for partial
credit.
-Significant figures and
units will be graded throughout the exam.
1. (5 pts)
Explain the difference between a molecule and a compound.
2. (2 pts
each):
Give
the chemical formula for aluminum sulfide (a compound, not an ion).
What
is wrong with the following chemical formula?
Na2H2PO4
Name
or give the chemical formula for:
Iron
(III) chloride ___________________
Strontium
hydrogen phosphate _______________________
KMnO4
______________________________
Chloric
acid ________________________
Chromium
(VI) nitrate ____________________
Write
an equation (unbalanced or balanced), containing all reactants and products
for:
The
reaction of an alkaline earth metal with hydrochloric acid:
Carbon
dioxide and water
A
hydrocarbon, say CH4 (methane), combusted in air
3. (5 pts)
What is the conceptual basis behind the amu? (What does it do for us?)
What
is the basis behind the exact numerical value of the amu?
4. (15 pts) When limestone, CaCO3, is heated
it decomposes to form CO2 and lime, CaO. If you decompose 1.000 kg of limestone, how much of each
product will you theoretically produce?
Solve this problem by constructing a complete flow chart.
5.
(20 pts) Gasoline that is burned in cars typically
contains C-8 hydrocarbons; a generic C-8 hydrocarbon is isooctane, C8H18. When an engineer designs the combustion
cylinder in a car they would ideally like all reactants to be there in perfect
stiochiometric amounts. If an
apprentice engineer designs a Òtest burnÓ and introduces 150. grams of
isooctane and 30.5 grams of O2, determine if a perfect stiochiometic
ratio is present. If not, which
reactant is the limiting reagent? Next, create a complete flow chart, based on
your limiting reagent, illustrating the masses and moles of each reactant and
product.
6. (15 pts) Determine the empirical formula for a
compound with the following elemental composition:
C =
21.7 % O
= 9.6 % F
= 68.7 %
7. (10 pts) Mercury has 7 stable isotopes as follows
Isotope Percent
Abundance
196 0.15
198 10.0
199 16.9
200 23.1
201 13.2
202 29.8
204 6.85
Confirm
or dispute the gram atomic weight shown in the attached Periodic Table.
8. Atomic Theory (2 pts each):
Dalton
stated that ÒAtoms of an element are not changed into different types of
atoms by reactions; atoms are neither created nor destroyed in reactionsÓ
a)
What fundamental law did this evolve into?
b) ThereÕs one exception to this law; what
is it?
J.J.
Thompson devised the ÔPlum PuddingÓ model of the atom.
a)
Who disproved this model?
b)
Very briefly (no pictures are necessary) describe how he did this.
J.J.
Thompson experimented with the cathode ray tube, a precursor to the television
tube.
a) What two discoveries/observations can
out of these experiments?
1)
2)