ENGR 121
EXAM 1 Name:
________________________________
Closed book, closed notes.
Honor Statement: On my honor, I promise that I have not received any outside assistance on this exam (I didn’t look at another
student’s paper, I didn’t view any unauthorized written materials, I didn’t talk or listen to another student). I also promise not to
discuss the exam with students in other sections until after all sections have taken the exam.
___________________________________________signature
1 Coulomb = 6.24(10)18 electrons
Avogadro’s Number: 6.022(10)23
1 metric ton = 1000 kg
Atomic Weights: Na = 23.0 g/mol, Cl = 35.5 g/mol, C = 12.0 g/mol, H = 1.0 g/mol, O = 16.0 g/mol
Density of water at 4oC (maximum density) = 1 g/ml = 1g/cm 3 = 1kg/L = 1000 kg/m3 = 8.33 lbs/gal
1L = 0.001m3 = 1.0567quarts = 0.264gal = 61.02in3
−
Conductivity Sensor Reactions: 2𝐶𝑙(𝑎𝑞)
→
1 gal = 0.1337 ft3 1 pound = 453.592 grams
𝐶𝑙2 (𝑔) + 2𝑒 − and
Volume of Cylinder =
2𝐻2 0(𝑙) + 2𝑒 − →
𝜋∙𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟2
4
1 inch = 25.4 mm
−
𝐻2 (𝑔) + 2𝑂𝐻(𝑎𝑞)
∙ ℎ𝑒𝑖𝑔ℎ𝑡
1. (2 points) The object shown to the right was used when you fabricated the
wooden fishtank platform. It is called a ____________ _____________.
(provide the two words used in the PowerPoint presentation if you know them).
2. (2 points) The black screws used to join the wooden pieces together when
fabricating the fishtank platform are called __________________ screws.
3. (2 points) Ultra High Molecular Weight Polyethylene was used to fabricate the conductivity sensors.
The PowerPoint presentation showed that polyethylene molecules are long, chain-like molecules made
from what two atoms? ______________ and ______________
4. (2 points) The 1/16 inch diameter rod used to make the metal probes for the conductivity sensors was
made from 316 _______________ ______________.
5. (2 points) Recall how you used a lathe to center-drill a hole through your polyethylene conductivity
sensor. The Q bit was held stationary using a drill chuck mounted to a part of the lathe called the
_ _ _ _stock. (hint: most dogs have one of these)
6. (2 points) The process of cutting internal threads is called _______ing. You performed this operation
when you cut threads into your fishtank and into your conductivity sensor.
7. (2 points) You used two liquids to bond the PVC cap to the 3-inch long PVC pipe segment when
making you fishtank. What was the purpose of the first liquid that was applied?
___________________________________________________________
8. (2 points) Oxidation occurs at the anode and reduction occurs at the cathode. At which electrode (the
anode or the cathode?) is water broken up into OH- and H? ____________________
9. (2 points) We used DI water for the fishtank project. DI stands for _________________.
10. (2 points) The picture shown is of what famous scientist (it was in the notes)?
_____________________________________ (last name is OK).
11. (2 points) The base material used for most semiconductors is ______________ (the name of the
atom that forms the main ingredient of semiconductors).
12. (2 points) In class, we talked about doping a semiconductor with phosphorus (5 valence electrons)
and with boron (3 valence electrons). Doping with boron will cause the resulting semiconducting
material to have a missing electron which is often called a ___________.
13. (2 points) What type of relay is depicted in this image?
___________ pole ____________ throw
14. (2 points) The power used to energize the coil on the relay (thus closing the contacts) comes from
which source? Please be very specific.
15. (2 points) The difference between the UCL and the LCL is called the _ _ _ _band.
16. (2 points) After a solenoid valve is opened and closed, it takes some time for the system to settle out
to equilibrium. The ______________ _________________ is set to allow the fishtank system to come
to equilibrium before responding to error (before opening up another solenoid valve).
17. (2 points) How far above the setpoint is UCL? Provide a one sentence answer.
18. (2 points) Overcorrecting the salinity (adding too much salty or DI water) can cause the salinity to
overshoot the setpoint. Repeatedly overcorrecting the salinity can cause the salinity values in the
fishtank system to __________ about the setpoint.
19. (2 points) The ________ is a proportionality constant that is set to correct the salinity from a current
value to a value that is in the direction of the setpoint (but not all the way to the setpoint). We used a
value such as 0.8 for our analysis.
20. (2 points) We purchased our SPST relays from a company called ____________.
21. (5 points) A fishtank with a diameter of 1.6 inches and a depth of 2.4 inches contains a mass of water
closest to
(a) 56 grams
(b) 70 grams
(c) 79 grams
(d) 88 grams
(e) 94 grams
22. (5 points) If 40g of NaCl is completely hydrated in water, the number of Cl - ions in the resulting
solution is closest to
(a) 1.99 (10)23
(b) 2.06 (10)23
(c) 2.78 (10)23
(d) 3.49(10)23
(e) 4.12(10)23
23. (5 points) The mass of NaCl that you would need to add to 5 kg of water to create a concentration of
0.15% NaCl is closest to
(a) 1.8 g
(b) 7.5 g
(b) 43 g
(c) 94 g
(d) 107 g
(e) 521 g
24. (5 points) A mass of 400g of salt is poured into 1 gallon of water. The resulting salinity of the water
in % wt NaCl is closest to
(a) 5.8% wt NaCl
(b) 9.6% wt NaCl
(c) 11.7% wt NaCl
(d) 13.2% wt NaCl
(e) 15.9% wt NaCl
25. (5 points) A batch of masonry cement is made by 15 gallons of wet sand with one 70 lb. bag of
masonry mix and 2 gallons of water. The sand used in the mix is partially wet, containing an unknown
amount of water. If the final batch of “mud” contains 13% water when the desired consistency is
reached, then how many gallons of water did the sand used in the mixture contain? Assume that the
density of dry sand is 111 lbs/ft3 and that wet sand and dry sand occupy the same volume.
(a) 1.7 gal
(b) 2.1 gal
(c) 2.9 gal
(d) 3.2 gal
(e) 4.4 gal
26. (5 points) A constant current of 5mA passes through the probes of a conductivity sensor. The
number of Cl2 molecules formed over a 10 second period is closest to . . .
(a) 8.2(10)15 Cl2 molecules
(b) 4.7(10)16 Cl2 molecules
(c)9.4(10)16 Cl2 molecules
(d) 1.6(10)17 Cl2 molecules
(e) 9.9(10)17 Cl2 molecules
27. (5 points) Broken Bow, Oklahoma, primarily gets its water supply from the local water tower. The
water is collected in a large tank and processed through a filtration system before being distributed
through the town’s Water Works Division. It’s known that the rain water collected in the tank consists of
97% pure water, 1% minerals, and 2% other materials (such as leaves). Some water is lost through
evaporation. The filtration process creates a waste consisting of 30% water, 2% minerals, and 68% other
materials. The drinkable water remaining after filtration consists of 99% pure water and 1% minerals. If
the town needs 90,000 lb of water each week, how much rain water (by mass) must be collected weekly
in the water tower?
(a) 90,800 lbs
(b) 92,400 lbs
(c) 95,600 lbs
(d) 97,300 lbs
(e) 99,900 lbs
28. (5 points) A chamber with a diameter of 100mm is filled to depth of 200mm with water containing
0.1% wt NaCl. We wish to increase the salinity to 0.15% by adding salt water from a “salty tank” with a
5% wt NaCl solution.
When water from the “salty tank” is added, an equal volume of water must leave the chamber through
the overflow; please assume that the same mass of water that enters from the “salty tank” leaves
through the overflow.
If 50% of the water leaving through the overflow comes directly from the “salty tank” and the remainder
that leaves is 0.1% wt NaCl, then the mass of “salty tank” water that should be added is closest to . . .
(a) 32g
(b) 37g
(c) 41g
(d) 45g
(e) 49g
29. (5 points) The nutritional facts for Gatorade sports drink are shown below for a 0.24L serving. The
human body’s absorption efficiency, body content for a 70kg person, and mineral loss due to sweating
are summarized in the table to the right.
In this problem, we will assume that sweat and Gatorade both have density of 1kg/L.
If a 70kg athlete with loses 4L of fluids through sweating while taking in 1L of Gatorade. We would like
to estimate the athlete’s sodium content after sweating. Assume that the absorption efficiency for
sodium is 90% (only count the portion that is absorbed) and that the sweat leaving the athlete has a
concentration of 1500 mg/L. The athlete’s final content of sodium is closest to . . .
1,000,000 mg = 1,000 g = 1kg
(a) 83,200 mg sodium
(b) 84,400 mg sodium
(c) 85,600 mg sodium
(d) 87,200 mg sodium
(e) 88,900 mg sodium
and 1,000mL = 1L (ml from the Gatorade label = mL)
ENGR 121
Exam 1
Name: __________________________
Computer Portion: Allowed materials include calculator and computer, Boe-Bot, multimeter, pen or pencil.
Honor Statement: On my honor, I promise that I have not received any outside assistance on this exam (I didn’t look
at another student’s paper, I didn’t view any unauthorized written materials, I didn’t talk or listen to another student,
my network connectivity was not turned on, . . .).
___________________________________________signature
Please raise your hand after finishing each problem.
1. The assembly below is made up of two distinct parts, where all dimensions are in inches.
cap:
tube:
2 inch outer radius, 1.5 inch inner radius, 2 inches tall, 1.5 inches deep (the bottom is ½ inch thick)
1.5 inch outer radius, 1 inch inner radius, 4 inches tall
□ (5 points) Show your instructor the assembly.
□ (5 points) Show your instructor the exploded assembly. Two distinct parts should be visible.
(a) cap
(b) tube
PROBLEM 2 IS ON BACK – FLIP OVER PAPER
2. Incorporate the fitting below into the fishtank assembly drawn for problem 1. Cut a hole into the “fishtank” for the
fitting to pass through.
□ (2 points) Show your instructor the part shown to the right above.
□ (3 points) Show your instructor an exploded view of the assembly (with the hole in the fishtank showing).