Docsity
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Docsity AI
Docsity AI
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

Practice Problems - Engineering Sustainability | ENCE 215, Study notes of Civil Engineering

University of MarylandCivil Engineering
Prof. Allen P. Davis

Practice Problems Material Type: Notes; Professor: Davis; Class: ENGR SUSTAINABILITY; Subject: Engineering, Civil; University: University of Maryland; Term: Fall 2012;

Typology: Study notes

2011/2012

Uploaded on 09/05/2012

soccerslov5
soccerslov5 🇺🇸

5

(1)

28 documents

1 / 7

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
ENCE 215 Engineering for Sustainability Supplemental Problems
1. Estimate the population of a community in 2030, knowing that the population in 2010 is 35,600. The
population is growing exponentially, with r=0.023 yr-1.
2. The doubling time of a population is 34 years. The current population in 2010 is 78,400. What is the
expected population in 2025?
3. A population is following a logarithmic (restricted) growth, or S curve. The population carrying capacity is
350,000. The population in 2010 is 251,000 and that in 2000 was 238,000. What is the population
growth rate?
4. 1 MJ (106 J) of heat energy is added to volume of water. The temperature of the water increased from 15
to 25°C. What volume of water was heated?
5. A small lake is approximately round, average depth of 4 m, diameter of 300 m. At sunrise the lake
temperature is 11°C. During the hot summer day, the lake absorbs 8x1012 J of heat energy. What is the
temperature the lake at the end of the day?
6. How much power is required to melt 10 kg of ice in 1 hour? The ice is initially at -10°C and at the end is
completely melted at 0°C.
7. An aluminum rod, mass of 40 kg, temperature of 80°C, was placed in 20 L of water, with 5 kg of ice, both
at 0°C. What is the temperature of the water + Al system after reaching thermal equilibrium?
8. In the box below, write a balanced equation for the combustion of octane, C8H18.
W
Yr-1
W
°C
pf3
pf4
pf5

Partial preview of the text

Download Practice Problems - Engineering Sustainability | ENCE 215 and more Study notes Civil Engineering in PDF only on Docsity!

ENCE 215 Engineering for Sustainability Supplemental Problems

  1. Estimate the population of a community in 2030, knowing that the population in 2010 is 35,600. The population is growing exponentially, with r=0.023 yr -^.
  2. The doubling time of a population is 34 years. The current population in 2010 is 78,400. What is the expected population in 2025?
  3. A population is following a logarithmic (restricted) growth, or S curve. The population carrying capacity is 350,000. The population in 2010 is 251,000 and that in 2000 was 238,000. What is the population growth rate?
  4. 1 MJ (10^6 J) of heat energy is added to volume of water. The temperature of the water increased from 15 to 25°C. What volume of water was heated?
  5. A small lake is approximately round, average depth of 4 m, diameter of 300 m. At sunrise the lake temperature is 11°C. During the hot summer day, the lake absorbs 8x10 12 J of heat energy. What is the temperature the lake at the end of the day?
  6. How much power is required to melt 10 kg of ice in 1 hour? The ice is initially at -10°C and at the end is completely melted at 0°C.
  7. An aluminum rod, mass of 40 kg, temperature of 80°C, was placed in 20 L of water, with 5 kg of ice, both at 0°C. What is the temperature of the water + Al system after reaching thermal equilibrium?
  8. In the box below, write a balanced equation for the combustion of octane, C 8 H 18.

W

Yr -

W

°C

  1. Given following eqn, how much carbon dioxide (kg) is produced by the combustion of 200 kg of the fuel.

C2H 5 OH + 3 O 2 W + 2 CO 2 + 3H 2O

  1. How many kg of CO 2 are released from the combustion of 57 kg of octane (C 8 H 18 )?
  2. How much sucrose sugar (C 12 H 22 O 11 ) is produced from 100 kg of carbon dioxide via photosynthesis? Equation below is unbalanced.

CO 2 + H2O W C12H 22 O 11 + O 2

  1. The combustion of two moles of fuel releases 6180 kJ of heat. Given following eqn, find the enthalpy of formation (kJ/mol) for the fuel.

C5H 12 O + 7.5 O 2 W + 5 CO 2 + 6H 2O

  1. How much coal must be combusted to produce 100,000 kJ of energy?
  2. Find the energy absorbed (in kJ) during the synthesis of 45 kg of simple sugar (C 6 H 12 O 6 ) via photosynthesis. ΔHf^0 (C 6 H 12 O 6 )=-1275 kJ/mol.
  3. A desirable goal is to obtain an average of 80,000 W of energy from a building rooftop in MD using an array of solar cells. The building is 8 m tall, 40 m wide, 80 m long. What photovoltaic efficiency is necessary to meet this goal?
  4. Our calculations show that a car tank of gasoline contains approximately 2x10 6 J of potential energy. How much stored water is needed at a 2 m head to produce this much potential energy?

kg

kJ/mol

L

kg

kg

  1. A table showing average temperatures in a city is given below. Find the number of heating degree days (HDD) represented by these data. Day Average Temperature (°F) 1 56 2 58 3 63 4 57 5 52 6 49 7 51
  2. A moderate-sized office building is planned for construction in College Park. We know that the heating degree days is 2430 °C-days. The building shell dimensions will be 10 m tall, 60 m wide and 80 m long (flat roof). The total conduction parameter (d/k) is estimated at 2.5 m^2 - °K/W (including air films). Heat loss via conduction from the bottom of the building is negligible. The building is designed for 0.8 air changes per hour. What is the expected yearly energy requirement for heating?
  3. A 2 m^2 work area must be illuminated at 600 lux with fluorescent lighting. What is the energy use for 10 hours of operation?
  4. For an electrochemical reaction involving Zn (s) /Zn 2+ (aq) and Fe (s) /Fe2+ (aq) : a. Write the thermodynamically favorable reaction in the box below.

b. Find the standard potential for the reaction

c. What is n , the number of electrons transferred?

  1. A redox system consists of Ni 2+/Ni and Zn 2+/Zn. Write the thermodynamically favorable reaction and the potential under standard conditions.

V

W

n=

J

J

°F-days

Reaction: V

  1. How many kg of Li will be reacted to produce a current of 2.4 A (coul/s) for 2 days?
  2. A collection of electrical cells are stacked so that a battery will produce a potential of 85 V. How much current is employed if the battery supplies 150 W?
  3. A nickel-cadmium battery (Ni (^) (s)/Ni 2 , Cd (^) (s)/Cd 2+) uses 0.1 grams of nickel (Ni) in the production of 1650 J of energy under non-standard conditions. What is the voltage of the battery?
  4. A community has a population of 23,000 over an area of 16 ha. If the population is growing at a rate of 4.2% each year, how long would it take to reach a population density of 4000 people per ha.
  5. For a population density of 4000 people per ha over 16 ha, how much drinking water must be supplied to this community?
  6. What is the probability of getting at 20-yr storm during any given year?
  7. The makeup of a water containing a mixture of salts is given in the table below. Fill in the missing concentration.

Ion Concentration (M) Ion Concentration (M) Mg2+^ 0.1 SO 4 2-^ 0. Ca 2+^ 0.2 Cl-^ _______ Na +^ 0.

yrs

Gallons/day

Volts

Amps

  1. A wastewater that contains Cr 3+^ is treated via pH adjustment to precipitate the Cr as Cr(OH) 3 (s). The pH has been adjusted to 5.8. What should be the concentration of residual Cr 3+^ at equilibrium ( in mg/L )?
  2. A system is evaluated with chlorine (Cl 2 /Cl -^ ) and nickel (Ni/Ni 2+^ ) at 25°C. When the chlorine gas partial pressure is 0.01 atm and dissolved chloride is present at 5x10 -3^ M, the redox potential is 1.81 Volts. What is the Ni 2+^ concentration?

mg/L

M