ENGR 121
Section______ Instructor:_____________ Name: ____________________________
Form#: 22
Allowed materials include calculator (without wireless capability), pencil or pen.
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, . . .).
___________________________________________signature
4 1 2 1
H11
H12
H13
H14
001
002
003
004
8-9:50 TR
2-3:50 TR
2-3:50 MW
10-11:50 MW
8-9:50 MW
10-11:50 MW
10-11:50 TR
12-1:50 TR
Hall
Cronk
Swanbom
Watson
Barker
Crittenden
Watson
Barker
also fill in CWID, name and course (121) . . . don’t forget to black in bubbles
you must show your work on problems that require calculations to receive credit
Problem 1
(3 points) The body of the conductivity sensor (the part water flows through) is made of . . .
a. PVC
b. ultra high molecular weight polyethylene
c. stainless steel
d. nylon
e. ABS
Problem 2
(3 points) Identify two doping agents commonly used to make a transistor:
a. boron & silicon
b. bromine & platinum
c. phosphorus & silicon
d. platinum & boron
e. boron & phosphorus
f. all of the above
g. none of the above
Problem 3
(3 points) In class, you used a transistor to make an LED turn light up by issuing certain commands
from your Arduino. Which of the commands below is one that would be essential?
a. digitalRead()
b. digitalWrite()
c. Serial.begin()
d. servo()
e. analogRead()
f. analogWrite()
g. Serial.print()
Problem 4
(3 points) The name of the company where the relay was purchased is . . .
a. Jameco
b. Digikey
c. Jameco
d. MPJA
e. McMaster
f. Walmart
g. KFC industrial
h. Tolliver
Problem 5
(3 points) Identify the type of relay used for the fish tank project:
a. SPST
b. SPDT
c. DPST
d. DPDT
e. all of the above
f. none of the above
Problem 6
(3 points) When using a lathe, the cutting tool is mounted to the top of an assembly of parts called
the . . .
a. tailstock
b. spindle
c. chuck
d. carriage
e. rail
Problem 7
(3 points) When using the LCD to display the status of your fishtank system, information is sent to
the LCD from the Arduino using . . .
a. an analog pin configured as an input
b. an analog pin configured as an output
c. a digital pin configured as an output
d. a digital pin configured as an input
e. the USB cable
Problem 8
(3 points) What would an LCD read if you created an Arduino sketch using the code below. You
may assume that the code is working correctly, and that the BYTE values correctly position text
on the screen.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
OUTPUT
ANALOG INPUT
raw=
BYTE
volts=
LED=
a & d only
b, c, e, & f only
All of the above
None of the above
Problem 9
(3 points) The source of the electrical power that flows through the solenoid valve to close the valve
comes from . . .
a. a digital pin on the Arudino
b. the 5V pin on the Audino
c. the 12V power supply connected to the wall
d. Vin on the Arduino
e. your computer
f. all power comes from the sun
HINT: Some electrons actually pass through the solenoid valve . . . where do they come from?
Problem 10
(5 points) How much DI water must be added to a container with 50 kg of a 2% NaCl solution to
achieve a 0.10% NaCl solution?
a.
b.
c.
d.
e.
f.
g.
h.
10 kg
50 kg
100 kg
500 kg
667 kg
895 kg
950 kg
1000 kg
Problem 11
(5 points) 20 kg of water is evaporated from a vat that contains 200 kg of an 11% brine solution
(11% salt; 89% water). 5 kg of salt is then added to the brine. The brine solution that results from
this process will contain what percentage of salt?
a.
b.
c.
d.
e.
f.
g.
h.
i.
3%
10%
12%
15%
18%
29%
35%
89%
100%
Problem 12
(5 points) A fishtank reservoir has an inside diameter of 1.75 inches. The water level inside the
reservoir is 2.25 inches high. The mass of water in the reservoir is closest to…
a.
54 g
b. 0.089 g
c.
5.4 g
d. 88,685 g
e. 543 g
f.
88.7 g
g.
50.7 g
h. 5.0 g
Problem 13
(5 points) Two (2) kilograms of deionized water is mixed with 225 grams of NaCl. The percent weight
of NaCl for this mixture is closest to…
a.
1.13 %
b. 14.6 %
c.
1.01 %
d. 9.9 %
e. 11.25 %
f.
8.9 %
g.
10.1 %
h. 12.4 %
Problem 14
(5 points) A mixture whose % weight of NaCl is 14.25% is required for a project. The amount of NaCl
that must be added to 5 liters of deionized water in order to achieve this % weight is closest to…
a.
5.83 kg
b. 0.83 kg
c.
4.29 kg
d. 0.7125 kg
e. 0.021 kg
f.
2.15 kg
g.
3.109 kg
h. 0.413 kg
Problem 15
(5 points) A batch of concrete has been mixed in a container. The mass of concrete (mix and
water) in the container is 46.25 kg. The concrete is composed of 75% mix and 25% water, by
weight, and is too wet. The desired composition is 85% mix and 15% water. Assuming you
could remove the excess water, the amount of water that you would remove to achieve the
desired composition is closest to …
a.
34.69 kg
b. 7.21 kg
c.
6.12 kg
d. 11.56 kg
e. 5.44 kg
f.
6.94 kg
g.
4.625 kg
h. 2.76 kg
Problem 16
(5 points) The average value of a set of salinity readings is 375. The standard deviation of these
values is 10. The minimum value of the readings is 351 and the maximum value of the readings is
397. If the target salinity is set to 375, then the UCL is closest to . . .
a. 315
b. 375
c. 385
d. 395
e. 405
f. 415
g. 475
Problem 17
(5 points) Assume the setpoint for your salinity control system is 0.08 wt% NaCl, the UCL is 0.10 wt%
NaCl, and the LCL is 0.06 wt% NaCl. Assuming the current salinity is 0.19 wt% NaCl and you operate
your control system with a gain of 0.7, then the target salinity is closest to . . .
a. 0.060 wt% NaCl
b. 0.072 wt% NaCl
c. 0.100 wt% NaCl
d. 0.113 wt% NaCl
e. 0.138 wt% NaCl
f. 0.151 wt% NaCl
g. 0.180 wt% NaCl
Problem 18
(5 points) Assume that a cylindrical tank of water 1 meter in diameter and 2 meters tall contains salt
water with a concentration of 0.11% NaCl by weight. You would like to add the correct amount of
1% NaCl to bring the concentration to 0.15% NaCl. However, when you add a certain mass of salt
water, and equal mass of water leaves the system through an overflow. If 15% of the overflow is 1%
NaCl and the rest is 0.11% NaCl, then the amount of 1% NaCl salt water that you should add to your
system is closest to . . .
a. 1.2 kg
b. 4.8 kg
c. 9.1 kg
d. 18.7 kg
e. 29.0 kg
f. 52.8 kg
g. 83.1 kg
h. 157.1 kg
Problem 19
(5 points) Two small fresh water streams are routed through alligator sculptures so they dump into
the salt water pool of a wealthy engineering professor; pool dimensions are shown below. Assume
that the target salinity of the water is 0.5% NaCl by weight, the flow rate of stream 1 is 5kg/min, and
the flow rate of stream 2 is 6 kg/min. Water drains from an overflow so that the level in the pool
remains constant; assume that the overflow has a concentration of 0.45% NaCl. The rate that dry
salt must be added to the pool to maintain the target salinity is closest to . . .
a. 0.04 kg/min
b. 0.05 kg/min
c. 0.06 kg/min
d. 0.10 kg/min
e. 0.20 kg/min
f. 0.50 kg/min
g. 1.0 kg/min
Problem 20
(5 points) The circuit shown is set up to measure the conductivity of 0.05% salt
water. For this salt concentration, the effective resistance across the electrodes of
the conductivity sensor is 15kΩ. If 5V is supplied across the entire circuit as shown
for 10 minutes, the number of moles of chlorine gas molecules that will be produced
in the resulting electrochemical reaction is closest to:
a. 0.120
b. 7.5 x 1017
c. 3.7 x 1017
d. 1.24 x 10-6
e. 6.2 x 10-7
f. 1.04 x 10-6
g. 1.55 x 10-6
h. 1.04 x 10-8
Problem 21
(5 points) Suppose you want your car to produce hydrogen gas to mix with other fuel that the engine in
your car burns. You plan to use electrical current from the alternator of the car to electrolyze salt water
(the same reactions as the ones that take place at the electrodes of your conductivity sensor). If you
want to produce 0.18 grams of hydrogen gas every minute, the electrical current required from the
alternator is closest to:
a. 7.28A
b. 28.7A
c. 72.8A
d. 287A
e. 728A
Problem 22
(5 points) You are drying your clothes and realize that this is a material balance problem! So for
your next load you decide to calculate how much water is removed from your T-shirts as they
dry. You have 10 shirts and your pocket hydrometer tells you that they are 27% water when
you take them out of the washing machines spin cycle. After drying, your hydrometer tells you
that the T-shirts are only 2% water and a Google search tells you that the average T-shirt
weighs 150 grams. The amount of water removed from the T-shirts during the drying process
is closest to:
a.
b.
c.
d.
e.
f.
0.514 gallons
2.514 gallons
0.136 gallons
2.136 gallons
0.832 gallons
2.832 gallons
Problem 23
(5 points) You are trying to eat healthier as part of your New Year’s resolution. So you
decided that you will replace any whole milk in your diet with skim milk. Looking into the
process you find that Skim milk is made by removing some of the fat from whole milk.
The skim milk at your local store is 90.9% water, 9% protein and carbohydrates, and 0.1%
fat. If the original milk contained 4.5% fat, then the percentage of water in the whole
milk is closest to:
(Assume an amount of 1 kg of skim milk and assume that only fat was removed from the
whole milk.)
a.
b.
c.
d.
e.
f.
g.
h.
i.
92.9% water
90.9% water
88.9% water
86.9% water
84.0% water
82.9% water
80.9% water
78.9% water
76.9% water
Problem 24
(5 points) The previous problem now has you wondering what they do with all that fat. You find
out that they make cream with it! A little investigation tells you that a nearby plant separates
whole milk at 4% fat into skim milk at 0.35% fat and cream at 55% fat. The plant uses a giant
centrifuge to accomplish the separation. In a typical 8 hour day they will run 50,000 kg of whole
milk through the continuous centrifuge. If this rate is maintained, the amount of cream you expect
this plant to produce each hour is closest to:
a. 46,660 kg/hr
b. 5,833 kg/hr
c. 3,340 kg/hr
d. 1,270 kg/hr
e.
418 kg/hr
f.
132 kg/hr
g.
33 kg/hr
h.
6 kg/hr
1 coulomb = 6.24(10)18 electrons
Avogadro’s Number: 6.022(10)23
Density of water at 4°C (maximum density) = 1 g/mL = 1g/cm3 = 1000 kg/m3 = 8.33 lbs/gal
1 L = 0.001 m3 = 1.0567 quarts = 0.264 gal = 61.02 in3
1 pound = 16 ounces = 453.592 grams
Conductivity Sensor Reactions:
2𝐶𝑙 −𝑎𝑞
𝐶𝑙2 (𝑔) + 2𝑒 − and
1 gal = 0.1337 ft3 = 3.785 L
1 inch = 25.4 mm
2𝐻20(𝑙) + 2𝑒 −
1 foot = 12 inch
−
𝐻2 (𝑔) + 2𝑂𝐻(𝑎𝑞)
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
Volume of Cylinder =
𝜋 ∙ 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 2
4
∙ ℎ𝑒𝑖𝑔ℎ𝑡
/*****************************************************************************/
/* A partial listing of commands recognized by the LCD is provided below.
*/
/* See the data sheet for the LCD on the Parallax web site for more details. */
/* Serial.write(8) - move cursor one space left
*/
/* Serial.write(9) - move cursor one space right
*/
/* Serial.write(10) - move cursor down one line
*/
/* Serial.write(12) - clear screen and move cursor to top left
*/
/* Serial.write(13) - carriage return (will wrap if on last line)
*/
/* Serial.write(17) - turn backlight on
*/
/* Serial.write(18) - turn backlight off
*/
/* Serial.write(21) - turn display off
*/
/* Serial.write(22) - turn display on, cursor off, no blink
*/
/* Serial.write(23) - turn display on, cursor off, character blink
*/
/* Serial.write(24) - turn display on, cursor on, no blink (default)
*/
/* Serial.write(25) - turn display on, cursor on, character blink
*/
/* Serial.write(128) moves the cursor to row 0 and position 0
*/
/* row and position commands are shown below for all 80 character positions */
/*
ROW 0:
128=(0,0) 129=(0,1) 130=(0,2) 131=(0,3) 132=(0,4)
*/
/*
133=(0,5) 134=(0,6) 135=(0,7) 136=(0,8) 137=(0,9)
*/
/*
138=(0,10) 139=(0,11) 140=(0,12) 141=(0,13) 142=(0,14)
*/
/*
143=(0,15) 144=(0,16) 145=(0,17) 146=(0,18) 147=(0,19)
*/
/*
ROW 1:
148=(1,0) 149=(1,1) 150=(1,2) 151=(1,3) 152=(1,4)
*/
/*
153=(1,5) 154=(1,6) 155=(1,7) 156=(1,8) 157=(1,9)
*/
/*
158=(1,10) 159=(1,11) 160=(1,12) 161=(1,13) 162=(1,14)
*/
/*
163=(1,15) 164=(1,16) 165=(1,17) 166=(1,18) 167=(1,19)
*/
/*
ROW 2:
168=(2,0) 169=(2,1) 170=(2,2) 171=(2,3) 172=(2,4)
*/
/*
173=(2,5) 174=(2,6) 175=(2,7) 176=(2,8) 177=(2,9)
*/
/*
178=(2,10) 179=(2,11) 180=(2,12) 181=(2,13) 182=(2,14)
*/
/*
183=(2,15) 184=(2,16) 185=(2,17) 186=(2,18) 187=(2,19)
*/
/*
ROW 3:
188=(3,0) 189=(3,1) 190=(3,2) 191=(3,3) 192=(3,4)
*/
/*
193=(3,5) 194=(3,6) 195=(3,7) 196=(3,8) 197=(3,9)
*/
/*
198=(3,10) 199=(3,11) 200=(3,12) 201=(3,13) 202=(3,14)
*/
/*
203=(3,15) 204=(3,16) 205=(3,17) 206=(3,18) 207=(3,19)
*/
/*****************************************************************************/