Chemistry in the Community Study Sheet Answers

Unit 4: Air--Chemistry In The Atmosphere

Section A: Gases In The Atmosphere (pp 248 - 271)

1)		Definitions (Look 'Em Up Yourself)
2)		Nitrogen (78 %), Oxygen (21 %), Water (~ 2 %), Argon (1 %)
3)	a)	Decreases (0 - 20 Km), Increases (20 Km - 50 Km), and Decreases (Above 50 Km)
	b)	Decreases
	c)	Decreases
	d)	Decreases
4)		4.5 atm = 460 KPa = 3400 mm Hg
		620 KPa = 6.1 atm = 4700 mm Hg
		220 mm Hg = 0.3 atm = 29 KPa
5)	a)	As pressure increases, volume decreases.
	b)
	c)	P1V1 = P2V2
	d)	19 mL
	e)	1.7 L or more correctly 1700 mL
	f)	1000 mm Hg
6)		37 oC + 273 = 310 K
		100 oC + 273 = 373 K
		20 K - 273 = -253 oC
		2588 K - 273 = 2315 oC
7)	a)	As temperature increases, volume increases.
	b)
	c)	V1 / T1 * = V2 / T2 * . . . . . * Remember . . . . temperatures must be in Kelvins!
	d)	2.8 L (Remember . . . . temperatures must be in Kelvins to perform the calculation.
	e)	1100 K or 850 oC
	f)	110 K or -160 oC
8)	a)	As temperature increases, pressure increases.
	b)
	c)	P1 / T1 * = P2 / T2 * . . . . . * Remember temperatures must be in Kelvins!
	d)	360 K or 91 oC (Remember . . . . temperatures must be in Kelvins to perform the calculation.
	e)	150 KPa
	f)	13 atm
9)	a)	3 mol CO2 = 132 g
		3 mol CO2 = 1.8 x 10 24 molecules
		3 mol CO2 = 67.2 L (at STP)
	b)	1 L N2 makes 2 L NH3 while 6 L H2 makes 4 L NH3

 

Section B: Radiation and Climate (pp 276 - 294 )

1)		Definitions - Look 'Em Up Yourself
2)		Gamma Rays, X Rays, Ultraviolet, Visible, Infrared, Radiowaves
3)		UV-B = E
		Wavelength = A
		Infrared = F
		Electromagnetic Spectrum = C
		UV-C = G
		Frequency = D
		UV-A = B
4)	a)	Most solar radiation (43 %) is absorbed and changed into thermal (heat) energy.
	b)	About 30 % of the solar radiation that reaches the earth is reflected directly to outer space.
	c)	Infrared radiation is produced as the surface of the earth warms up and radiates heat back out into the atmosphere.
	d)	Infrared radiation emitted by the earth is absorbed by greenhouse gases (CO2, CH4, H2O, etc.). This trapped heat results in the greenhouse effect.
5)	a)	Temp Change Water = 23.0 oC - 20.0 oC = 3.0 oC
	b)	Heat Absorbed By Water = 4.18 J / ( g oC) x 90.0 g x 3.0 oC = 11,000 J
	c)	Temp Change Metal = 100.0 oC - 23.0 oC = 77.0 oC
	d)	Specific Heat = 11,000 J / [16.4 g x 77.0 oC ] = 0.87 J / (g oC) ; Aluminum
6)	a)	Carbon is stored in the atomosphere (CO2), oceans, in the earth, and in organic matter.
	b)	Carbon enters the atmosphere through combustion, bacterial decay, plant respiration, animal respiration, and volcanoes.
	c)	Carbon leaves the atmosphere through photosynthesis, dissolving in ocean waters, and the death of animals and plants.
7)	a)	(i)You can only make 5 sandwiches.
		(ii) Cheese was what limited the number of sandwiches.
		(iii) 2 pieces of bread and 2 slices of ham are left over.
	b)	CH4 + 2 O2 CO2 + 2 H2O
	c)	(i) Three molecules of CO2 and six molecules of H2O are all you can make.
		(ii) The number of oxygen molecules limited the amount carbon dioxide and water.
		(iii) Three molecules of CH4 are left over.
8)	a)	Carbon dioxide--CO2 , methane--CH4, nitrous oxide--NO, CFCs, and even water--H2O are greenhouse gases.
	b)	Some impacts include raising the sea level, changing precipitation and other local climate conditions, altering forests, crop yields, and water supplies. It could also affect human health, animal populations, and cause deserts to may expand.

 

Section C: Acids In The Atmosphere (pp 297 - 312)

1)		Definitions (Look 'Em Up Yourself)
2)	a)	SO2 + H2O H2SO3
	b)	SO3 + H2O H2SO4
	c)	CO2 + H2O H2CO3
	d)	Sulfur oxides are produced mainly by coal burning power plants.
	e)	Nitrogen oxides are produced primaily by vehicles.
3)	a)	HCl + H2O H3O+ + Cl -
		HNO3 + H2O H3O + + NO3 -
		HC2H3O2 + H2O H3O + + C2H3O2 -
	b)	NaOH Na + + OH-
		Sr(OH)2 Sr 2+ + 2 OH-
		Al(OH)3 Al3+ + 3 OH-
	c)	HNO3+ NaOH H2O + NaNO3
		Ca(OH)2 + HC2H3O2 2 H2O + Ca(C2H3O2)2
		HCl + KOH H2O + KCl
4)	a)	.25 mol / 1.5 L = 0.17 M
		1.5 mol / x L = 0.75 mol / L ; x L = 2.0 L
		x mol / 3.00 L = .20 mol / L ; x mol = 0.60 mol
	b)	Conc H+ (M) 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 pH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Conc OH - (M) 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100
		If pH = 4, the H + = 10 -4 M, and the OH - = 10 -10 M.
		If H + = 10 -2 M, the pH = 2 and the OH - = 10 -12 M.
		If OH - = 10 -8 M, the pH = 4 and the H + = 10 -4 M.
		In a neutral solution, the H + = 10 -7 M, the OH - = 10 -7 M,and the pH = 7.
		In an acidic solution, the H + >10 -7 M, the OH - <10 -7 M and the pH < 7.
		In a basic solution, the H + < 10 -7 M, the OH - >10 -7 M and the pH >7.
		A solution with a pH = 2 is 1000 (10 3) times more acidic than a solution with a pH = 5.
	c)

 

Section D: Air Popllution--Sources, Effects, and Solutions (pp 315 - 333)

1)		Definitions (Look 'Em Up Yourself)
2)	a)	Sources of Primary Air Pollutants: Combustion of Fossil Fuels, Decomposition of Organic Matter, Nonnatural Chemicals Examples: CO, CO2, CH4, NOx, SO2, etc.
		Sources of Secondary Air Polutants: Reactions of Primary air pollutants othe pollutants or with natural components of air Examples: SO3 forms from SO2 and O2 . . . NO2 forms from NO and O2 . . . O3 forms from NO and O2
		Sources of Particulates: Power Plants, Waste Burning, Road Building, Forest Fires, Diesel Exhaust, etc. Examples: Smoke, Dust, Ash
		Synthetic Substances: Result of solely human activity
		Examples: CFCs
	b)	The most important source of  . . . carbon monoxide (CO) is transportation.
		. . . lead (Pb) is industrial processes.
		. . . nitrogen oxides (NOx) is transportation.
		. . . particulates is industrial processes.
		. . . electric power plants.
3)	a)	Hydrocarbons + O2 + CO + NOx O3 + NOx + Organic Cmpds + CO2 + H2O
	b)	N2 + O2 2 NO
		2 NO + O2 2 NO2
		NO2 + Sunlight NO + O
		O +  O2 O3
	c)	1st: NO, 2nd: NO2, 3rd: O3
4)	a)	Electrostatic Precipitation (Static electricity is used to collect charged particles.)
		Mechanical Filtering (A filter with small pores is used to collect particles too large to fit through the holes.)
		Scrubbing (Pollutants are bubbled through water. Pollutants are dissolved or trapped in the water.)
	b)	Exhaust Gases Products NOx N2 CO CO2 Hydrocarbons CO2 and H2O
5)		Natural Ozone Depletion: O3 + UV light O + O2
		Human Influenced Ozone Depletion: .Cl + O3 .ClO + O2 .ClO + O .Cl + O2
		.Cl atoms come from CFCs used as refrigerants and propellants.
		Hydrochlorfluorocarbons (HCFCs) are currently used and hydrofluorocarbons (HFCs) are being developed so that the effects of human influenced ozone depletion can be reversed.

 

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