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Problem 14
From the data in Table 18.1, calculate the partial pressures of carbon dioxide and argon when the total atmospheric pressure is 1.05 bar.
- The average concentration of carbon monoxide in the air in an Ohio city in 2006 was 3.5 ppm. Calculate the number of CO molecules in 1.0 L of this air at a pressure of 759 torr and a temperature of 22 °C.
Problem 15
- (b) What is the concentration of neon in the atmosphere in molecules per liter, assuming an atmospheric pressure of 730 torr and a temperature of 296 K?
Problem 16
Problem 17a
The dissociation energy of a carbon-bromine bond is typically about 276 kJ/mol. (a) What is the maximum wavelength of photons that can cause C-Br bond dissociation?
Problem 17b
The dissociation energy of a carbon-bromine bond is typically about 276 kJ/mol. (b) Which kind of electromagnetic radiation—ultraviolet, visible, or infrared—does the wavelength you calculated in part (a) correspond to?
- In CF3Cl, the C-Cl bond dissociation energy is 339 kJ/mol. In CCl4, the C-Cl bond dissociation energy is 293 kJ/mol. What is the range of wavelengths of photons that can cause C-Cl bond rupture in one molecule but not in the other?
Problem 18
Problem 19a
(a) Distinguish between photodissociation and photoionization.
Problem 19b
(b) Use the energy requirements of these two pro- cesses to explain why photodissociation of oxygen is more important than photoionization of oxygen at altitudes below about 90 km.
Problem 21a
The wavelength at which the O2 molecule most strongly absorbs light is approximately 145 nm. (a) In which region of the electromagnetic spectrum does this light fall?
Problem 21b
The wavelength at which the O2 molecule most strongly absorbs light is approximately 145 nm. (b) Would a photon whose wavelength is 145 nm have enough energy to photodissociate O2 whose bond energy is 495 kJ/mol? Would it have enough energy to photoionize O2?
Problem 22a
The ultraviolet spectrum can be divided into three regions based on wavelength: UV-A (315–400 nm), UV-B (280–315 nm), and UV-C (100–280 nm). (a) Photons from which region have the highest energy and therefore are the most harmful to living tissue? (315–400 nm), UV-B (280–315 nm), and UV-C (100–280 nm).
Problem 22b
The ultraviolet spectrum can be divided into three regions based on wavelength: UV-A (315–400 nm), UV-B (280–315 nm), and UV-C (100–280 nm). (b) In the absence of ozone, which of these three regions, if any, are absorbed by the atmo- sphere?
Problem 22c
The ultraviolet spectrum can be divided into three regions based on wavelength: UV-A (315–400 nm), UV-B (280–315 nm), and UV-C (100–280 nm). (c) When appropriate concentrations of ozone are present in the stratosphere, is all of the UV light absorbed before reaching the Earth’s surface? If not, which region or regions are not filtered out?
- Do the reactions involved in ozone depletion involve changes in the oxidation state of the O atoms? Explain.
Problem 23
Problem 24
Which of the following reactions in the stratosphere cause an increase in temperature there? (a) O(g) + O2(g) → O3+(g) (b) O3*(g) + M(g) → O3(g) + M*(g) (c) O2(g) + hv → 2 O(g) (d) O(g) + N2(g) → NO(g) + N(g) (e) All of the above
Problem 25
(a) What is the difference between chlorofluorocarbons and hydrofluorocarbons?
- Draw the Lewis structure for the chlorofluorocarbon CFC-11, CFCl3. What chemical characteristics of this substance allow it to effectively deplete stratospheric ozone?
Problem 26
- The average bond enthalpies of the C ¬ F and C ¬ Cl bonds are 485 kJ/mol and 328 kJ/mol, respectively. Given the fact that O2, N2, and O in the upper atmosphere absorb most of the light with wavelengths shorter than 240 nm, would you expect the photodissociation of C ¬ F bonds to be significant in the lower atmosphere?
Problem 27
- Would you expect the substance CFBr3 to accelerate the depletion of the ozone layer?
Problem 28
Problem 28a
(a) When chlorine atoms react with atmospheric ozone, what are the products of the reaction?
Problem 28b
(b) Based on average bond enthalpies, would you expect a photon capable of dissociating a C-Cl bond to have sufficient energy to dissociate a C-Br bond?
- Nitrogen oxides like NO2 and NO are a significant source of acid rain. For each of these molecules, write an equation that shows how an acid is formed from the reaction with water.
Problem 29
Problem 31a
(a) Write a chemical equation that describes the attack of acid rain on limestone, CaCO3.
Problem 31b
(b) If a limestone sculpture were treated to form a surface layer of calcium sulfate, would this help to slow down the effects of acid rain? Explain.
- The first stage in corrosion of iron upon exposure to air is oxidation to Fe2+. (a) Write a balanced chemical equation to show the reaction of iron with oxygen and protons from acid rain. (b) Would you expect the same sort of reaction to occur with a silver surface? Explain.
Problem 32
- Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH2O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photochemical smog: CH2O + hn → CHO + H. The maximum wavelength of light that can cause this reaction is 335 nm. (c) Compare your answer from part (b) to the appropriate value from Table 8.3. What do you conclude about the C−H bond energy in formaldehyde?
Problem 33
Problem 33b
Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH2O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photo- chemical smog: CH2O + hn ¡ CHO + H The maximum wavelength of light that can cause this reaction is 335 nm. (b) What is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 335-nm light?
Problem 33d
Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH2O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photo- chemical smog: CH2O + hn ¡ CHO + H The maximum wavelength of light that can cause this reac- tion is 335 nm. (d) Write out the formaldehyde photodis- sociation reaction, showing Lewis-dot structures.
Problem 34a
An important reaction in the formation of photochemical smog is the photodissociation of NO : NO2 + hv → NO(g) + O(g) The maximum wavelength of light that can cause this reac- tion is 420 nm. (a) In what part of the electromagnetic spec- trum is light with this wavelength found?
Problem 34b
An important reaction in the formation of photochemical smog is the photodissociation of NO : NO2 + hv → NO(g) + O(g) The maximum wavelength of light that can cause this reaction is 420 nm. (b) What is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 420-nm light?