Textbook Question
The concentration of H2O in the stratosphere is about 5 ppm. It undergoes photodissociation according to: H2O1g2 ¡ H1g2 + OH1g2 (b) Using Table 8.3, calculate the wavelength required to cause this dissociation.
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Ch.18 - Chemistry of the Environment
Chapter 18, Problem 85
The main reason that distillation is a costly method for purifying water is the high energy required to heat and vaporize water. (a) Using the density, specific heat, and heat of vaporization of water from Appendix B, calculate the amount of energy required to vaporize 1.00 gal of water beginning with water at 20 °C. (b) If the energy is provided by electricity costing $0.085/kWh, calculate its cost. (c) If distilled water sells in a grocery store for $1.26 per gal, what percentage of the sales price is represented by the cost of the energy?
Verified step by step guidance1
Step 1: Convert the volume of water from gallons to liters using the conversion factor 1 gallon = 3.78541 liters.
Step 2: Calculate the mass of the water using the density of water (approximately 1 g/mL or 1 kg/L) and the volume in liters.
Step 3: Calculate the energy required to heat the water from 20 °C to 100 °C using the formula q = mcΔT, where m is the mass of the water, c is the specific heat capacity of water (4.18 J/g°C), and ΔT is the temperature change.
Step 4: Calculate the energy required to vaporize the water at 100 °C using the formula q = mL, where m is the mass of the water and L is the heat of vaporization of water (2260 J/g).
Step 5: Add the energy calculated in steps 3 and 4 to find the total energy required, convert this energy from joules to kilowatt-hours (1 kWh = 3.6 x 10^6 J), and then calculate the cost using the given electricity rate of $0.085/kWh. Finally, determine the percentage of the sales price represented by the energy cost by dividing the energy cost by the sales price and multiplying by 100.
Related Practice
Open Question
Bioremediation is the process by which bacteria repair their environment in response, for example, to an oil spill. The efficiency of bacteria for 'eating' hydrocarbons depends on the amount of oxygen in the system, pH, temperature, and many other factors. In a certain oil spill, hydrocarbons from the oil disappeared with a first-order rate constant of 2 * 10 s. At that rate, how many days would it take for the hydrocarbons to decrease to 10% of their initial value?
Open Question
The standard enthalpies of formation of ClO and ClO2 are 101 and 102 kJ/mol, respectively. Using these data and the thermodynamic data in Appendix C, calculate the overall enthalpy change for each step in the following catalytic cycle: ClO(g) + O(g) → ClO(g) + O(g). What is the enthalpy change for the overall reaction that results from these two steps?
Open Question
A reaction that contributes to the depletion of ozone in the stratosphere is the direct reaction of oxygen atoms with ozone: O(g) + O3(g) → 2 O2(g). At 298 K, the rate constant for this reaction is 4.8 × 10⁵ M⁻¹ s⁻¹. Would you expect this reaction to occur via a single elementary process? Explain why or why not.
Textbook Question
The following data were collected for the desturction of O3 by H (O3 + H → O2 + OH) at very low concentrations (b) Calculate the rate constant
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Open Question
The degradation of CF3CH2F (an HFC) by OH radicals in the troposphere is first order in each reactant and has a rate constant of k = 1.6x10^8 M-1s-1 at 4 °C. If the tropospheric concentrations of OH and CF3CH2F are 8.1x10^5 and 6.3x10^8 molecules/cm3, respectively, what is the reaction rate at this temperature in M/s?