CHEM 302 Chapter Notes - Chapter 1: Piecewise Linear Function, Mixing Ratio, Photodissociation

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A weather station reports t = 293 k, rh = 50% at sunset. Assuming that ph2o remains constant, by how much must the temperature drop over the course of the night in order for fog to form: 2 phase partitioning of water in cloud. Consider the following typical vertical profile of ozone (o3) number densities measured over the united states. Ozone is produced in the stratosphere (10-50 km altitude) by photolysis of o2 and subsequent combination of o atoms with. The stratospheric o3 layer protects life on earth by absorbing solar uv radiation and preventing this radiation from reaching the earth"s surface. Fortunately, the o3 layer is not in contact with the earth"s surface; inhalation of o3 is toxic to humans and plants, and the u. s. environmental. Protection agency (epa) has presently an air quality standard of 80 ppbv o3 not to be exceeded in surface air.

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Assume you have a 20m x 100m greenhouse with 2.4m sidewalls, an open-gable interior roof and a roof at an 18.4 degree
angle (i.e., a typical 4â rise on 12â run roof line). You are growing plants that release into the greenhouse the equivalent
of 2500 gallons of liquid water/day-acre of growing area (in the form of water vapor). Additionally, the plants absorb
0.19 kg CO2/hr-100m2 of growing area. The ambient CO2 entering the greenhouse is 340 ppm. The outside air entering
the greenhouse through the ventilation system is 20oC and 50% RH. The greenhouse glass (R=0.8 m2-oC/W; air films NOT
included) receives 670 W/m2 of short-wave solar energy, 60% of which transmits through the glass where 30% of this
energy is absorbed within the greenhouse and used to heat the surrounding greenhouse air. You want to maintain the
following conditions: a). Inside temperature of the greenhouse no more than 10oC above ambient levels, b). CO2 inside
the greenhouse at 1200 ppm, during the 12 hours of daily sunlight, and c). the inside relative humidity at 70%.
1. (2) Determine the mass of water vapor produced in the greenhouse per second, hour, and day.
2. (2) Determine the mass flow rate of dry-air required to maintain the desired humidity ratio, W, in the greenhouse.
3. (4) Determine the mass of CO2 uptake by the plants to maintain photosynthesis per second, hour, and day.
4. (4) Using the mass flow rate of dry-air determined in (2), determine the amount of CO2 that must be added inside the
greenhouse to maintain the desired concentration of 1200 ppm.
5. (3) Determine the UA-value for the greenhouse.
6. (3) Determine the net solar energy absorbed inside the greenhouse that is available for sensible heating. Assume the
solar load is transmitting only through the roof surface area.
7. (4) Determine the mass flow rate of dry-air required to maintain the desired greenhouse air temperature.
8. (4) Assume that you want to ventilate the greenhouse at the larger of the rates determined for a water vapor balance
and energy (i.e., dry-bulb temperature) balance. At this rate, and using the CO2 generation rate determined in (4),
determine the resulting relative humidity, humidity ratio, dry-bulb temperature, and CO2.
9. (4) Plot using excel, the concentration of CO2 inside the greenhouse (in ppm) given the supply rate determined in (4),
as a function of the mass flow rate of dry-air through the greenhouse. Label the x-y axis (variable + units), use a scatter
graph, and label your legend. You are plotting CO2 concentration (y-axis) versus mass flow rate of dry-air (x-axis). You
will be graded on the accuracy of your solution and the professionalism of your plot.

1- (A) A 41 L cylinder containing helium gas at a pressure of 46.7 atm is used to fill a weather balloon in order to lift equipment into the stratosphere. To what maximum pressure (in atm) could a 286 L balloon be filled.

(B) A 38.0 L cylinder containing helium gas at a pressure of 20.9 atm is used to fill a weather balloon in order to lift equipment into the stratosphere. What is the final pressure (in atm) in the cylinder after a 169 L balloon is filled to a pressure of 1.15 atm.

(C)The following procedure provides a crude method of determining the molar mass of a volatile liquid. A liquid of mass 0.0181 g is introduced into a syringe and the end is capped (sealed). The syringe is transferred to a temperature bath maintained at 59.4 ^oC, and the liquid vaporizes. As the liquid vaporizes the plunger is pushed out. At equilibrium, the plunger reads 6.61 mL of gas. Atmospheric pressure is 740. mmHg. What is the approximate molar mass of the compound (in g/mol)?

(D)The reaction of magnesium metal with HCl yields hydrogen gas and magnesium chloride. What is the volume, in liters, of the gas formed at 757 torr and 34 ^oC from 4.59 g of Mg in excess Hal?

(E)What mass of water (in grams) forms from the reaction of 2.60 L of hydrogen gas and 1.97 L of oxygen gas? Both gases are at 698 torr and 12.9 ^oC.

(F)What is the partial pressure of argon, in torr, in a container that also contains neon at 220 torr and is at a total pressure of 439 torr?

(G)What is the total pressure if a container contains 10 torr of He gas, 207 torr of N₂ gas, and 72 torr of Ar gas?

(H)Oxygen gas is collected over water. The total pressure (the O₂ pressure + the water vapor pressure) is 760 torr. The temperature of the water is such that the water vapor pressure is 49 torr. What is the partial pressure of the oxygen gas in torr?

(I)A 5.10 L sample of neon at 10.11 atm is added to a 13.0 L cylinder that contains argon. If the pressure in the cylinder is 7.92 atm after the neon is added, what was the original pressure (in atm) of argon in the cylinder?

(J)Calculate the total pressure, in atm, in a 5 L flask that contains 6.42 g of Ne and 1.55 g of Ar. The temperature of the gases is 32 ^oC.

(K)Calculate v_rms, the root mean square velocity, in m/s of SO₂ molecules at 274 ^oC.

(L)An effusion container is filled with 7 L of an unknown gas. It takes 132 s for the gas to effuse into a vacuum. From the same container under the same conditions--same temperature and initial pressure, it takes 335 s for 7.00 L of O₂ gas to effuse. Calculate the molar mass (in grams/mol) of the unknown gas.

(M)Three bulbs are connected by tubing, and the tubing is evacuated. The volume of the tubing is 28.0 mL. The first bulb has a volume of 83.0 mL and contains 5.10 atm of argon, the second bulb has a volume of 250 mL and contains 1.09 atm of neon, and the third bulb has a volume of 33.0 mL and contains 4.04 atm of hydrogen. If the stopcocks (valves) that isolate all three bulbs are opened, what is the final pressure of the whole system in atm?

(N)Use the van der Waals equation to calculate the pressure, in atm, of 45.61 mol of hydrogen at 443 ^oC in a 2.45 L container.

CHEM 302 Chapter Notes - Chapter 1: Piecewise Linear Function, Mixing Ratio, Photodissociation

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