Register

Homework Help Question and Answers

Submit a new Query

Recent Homework Help Question & Answers


Question 45048

posted 10 months ago

The population of the world in 1800 was 0.9 billion.
a. What exponential rate of growth would have resulted in the population in 1960, which was 3billion? (Answer:r = 7.5*103 yr')
b. At this growth rate, what is the doubling time for this population? (Answer: Td = 92.4 yrs)
C.If this rate continued, what would the population have been in the year 2015?
d. Is your answer for part c) larger or smaller than the actual world population in 2015? What does this result mean in terms of how the rate of growth changed between 1800-1960 and1960-2015?

View answer

Question 45051

posted 10 months ago

Acid dissociation constant, Ka. (+3.5) An acid mine drainage treatment system in Pittsburgh,Pennsylvania, is being rehabilitated due to low treatment efficiency. Engineers want to know the concentration of metals in the sediment of the final settling basin. A 2 mg/L nitric acid (HNO3) is used-in a microwave digest or to solubilize the metals from the sediment before analysis. Assuming that the nitric acid reaction below is at equilibrium (pKa = -1.4), determine the pH of the solution. (Answer:pH=1.55)
\mathrm{HNO}_{3} \leftrightarrow \mathrm{H}^{+}+\mathrm{NO}_{3}^{-}

View answer

Question 45049

posted 10 months ago

Logistic Population Growth. (+4) Suppose the human population grows from 7 billion in 2010 to an ultimate population (i.e., carrying capacity) of 10 billion following the logistic growth curve with an instantaneous growth rate of 1.5 percent.
а.When will the world population reach 9 billion? (Answer: 2037)
b. What will the population be in 2050? (Answer: N = 9.45 billion = 9.45 x 10º)
b. What will the population be in 2050? (Answer: N = 9.45 billion = 9.45 x 10°)

View answer

Question 45050

posted 10 months ago

Calculate the THOD of 120 mg/L wastewater (C8H;O2N) assuming the following stoichiometry is valid.
\mathrm{C}_{8} \mathrm{HO}_{2} \mathrm{~N}+8 \mathrm{O}_{2} \rightarrow \mathrm{MH}_{3}+8 \mathrm{CO}_{2}+2 \mathrm{H}_{2} \mathrm{O}
\mathrm{NH}+2 \mathrm{O}_{2} \rightarrow \mathrm{NO}_{3}+\mathrm{H}+\mathrm{HzO}^{\mathrm{O}}

View answer

Question 45052

posted 10 months ago

5. Solubility product, Ksp. (+3.5) Engineers in South Africa are hired to determine whether a river that passes through a pyrochroite (Mn(OH)2) deposit meets the standards for drinking water (drinking water standard for Mn = 50 ppb). The river is in contact with solid Mn(OH)2 (pKsp = 14.3) and has apH of 8.0. Determine the concentration of Mn2+ in the river in mg/L. Also, determine the pH at which the concentration of Mn2* would meet the drinking water standard. (Answers: [Mn2*] = 275.2 mg/L;pH=9.87).
M n(O H)_{2} \leftrightarrow M n^{2+}+2 O H^{-}

View answer

Question 45053

posted 10 months ago

Henry's constant, KH. (+2) A biofuel researcher is running an experiment to produce methane from wastewater treatment plant sludge. The researcher places the sludge and a microbial inoculum into a sealed glass bottle rated to 20 psi, and is worried that if the pressure within the bottle becomes too high, that the glass may break. During the experiment, the aqueous concentration of methane in the closed bottle reaches 20 ppm. Determine the partial pressure of methane (PCH4) in the headspace at equilibrium if the KH,CH4 = 1.42 * 103 mol/L atm. Will the bottle break? (Answer: PCH4 = 0.88 atm).

View answer

Question 45261

posted 10 months ago

Problem 4 a) Determine the heat of vaporization of benzene at 25 °C using tabulated heats of formation.
b) Determine Henry's law constant of ammonia in water at 25 °C from the tabulated (g) and (ag) Gibbs energies of formation.
c) Generate an entry for the Gibbs energy of formation of CO based on the standard state for aqueous solutes
d) N2O gas is bubbled through water at 12 bar, 10 °C. Calculate the activity of N2O (aq) and of water (1) in the liquid based on the indicated standard states.

View answer

Question 45258

posted 10 months ago

Problem 1 A reactor is loaded with equal amounts of hydrogen, nitrogen, ammonia and helium. if thereaction is
3 \mathrm{H}_{2}+\mathbf{N}_{2}=2 \mathrm{NH}_{3}
a) Calculate the minimum and maximum values of .
b) Calculate all mole fractions when the mole fraction of helium is 0.3. What is the conversion of hydrogen?
c) Calculate all mole fractions when the mole fraction of helium is 0.215. What is the conversion of hydro-gen?

View answer

Question 45259

posted 10 months ago

Problem 2 Methane is mixed with 20% excess air at 1 bar, 25°C, and the mixture is ignited. Assuming complete oxidation to carbon dioxide and water, calculate the adiabatic temperature in the following tow cases:
a) Assume the heat capacities of all species to be constant and equal to their value at 25 °C.
b) Assume the heat capacities to be functions of temperature.

View answer

Question 45260

posted 10 months ago

Problem 3 a) Calculate the standard heat of reaction for the complete combustion of methane at 800 °C.b) Calculate the amount of heat that is released in a furnace that burns methane in 20% excess air, if the furnace temperature is 800 °C at the pressure is 2 bar. Assume that the inlet gases are already at 800°C asthe enter the furnace.
3 a) Calculate the standard heat of reaction for the complete combustion of methane at 800 °C.
b) Calculate the amount of heat that is released in a furnace that burns methane in 20% excess air, if the furnace temperature is 800 °C at the pressure is 2 bar. Assume that the inlet gases are already at 800°C asthe enter the furnace.
c) Repeat part b but this time the inlet gases are at 40°C, 2 bar.
Additional data: Assume that the reaction is complete and that products are carbon dioxide and water.The heat capacities of the gases are given in Problem ??.

View answer

Questions not Found

Most popular subject

Thermodynamics

Essay/Summary

Mechanics

Complex Analysis

Engineering Economics

Calculus

Modern Physics

General Chemistry

Strength Of Materials

Fluid Mechanics

x