CHEM 208 Lecture Notes - Lecture 8: Air Pollution, Bromine, Fluorine

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28 Jun 2018

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**Chem Chapter 8 Environmental

Concerns**

Acid Rain

-When atmospheric carbon dioxide dissolves in water it forms carbonic

acid

CO2(g) + H2O(l) -> H2CO3 (aq)

-The production of acid rain is due to the presence of the oxides of the

nonmetals nitrogen and sulfur

-The acid formed dissociates partially generating small amounts of

hydrogen ions

H2CO3 (aq) -> H+ (aq) + HCO3- (aq)

-The hydrogen ions formed are responsible for the weakly acidic nature

of rain

-weakly acidic nature of rain is due to dissolved CO2

The pH scale

-the acidity (a measure of hydrogen ion concentration) of a solution is

conveniently described in terms of pH scale

pH <7: solution is acidic

pH>7: solution is basic

pH=7: solution is neutral

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Laboratory Safety

-before working in a laboratory, you must be aware of Good laboratory

Practices (GLP)

-must also be aware of the Health and Safety aspects of the work you are

planning to carry out

-should be aware of carious hazards and the location of appropriate

control equipment, MSDSs, and personal protective equipment (safety

glasses, gloves, lab coat)

Determination of pH

-many neutral and synthetic dyes display different colors depending on

the pH of the solution and can be used as indicators for monitoring pH.

-vinegar (5% aqueous solution of acetic acid) pH <7 :acid

-water : pH +7 : neutral

-detergent: pH >7 : base

Higher Acidity = Lower pH

-based on the concentration of carbonic acid and small amounts of other

natural acids, the estimated pH of rain (as well as fog, dew and snow)

under normal atmospheric conditions should be around 5.3

-field measurements in many areas, on the other hand, show much

lower pH values (4.1-4.5)

-higher acidity ( lower pH) is due to the reactions of NOx and SOx present

in the atmosphere

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-various reactions of these oxides lead to the formation of acids

-the dissociation of formed acids generated hydrogen ions and hence

higher acidity (or lower pH)

-the reaction of limestone with HNO3 (aq) generates carbon dioxide

gaseous

-the reaction of limestone with H2SO4(aq) generates carbon dioxide

gaseous

-the reaction of limestone with an acid generates CO2 gaseous

2 SO2 (g) + O2 (g) + 2 H20 (l) -> 2 H2SO4 (aq)

H2SO4 (aq) -> H+ (aq) : HSO4- (aq)

HSO4- (aq) -> H+ (aq) : SO42- (aq)

4 NO2 (g) + O2 (g) + 2 H2O (l) -> 4 HNO3 (aq)

HNO3 (aq) -> H+ (aq) + NO3- (aq)

Environmental Effects

Material damage

-marble and limestone (CaCO3) used in many historic and irreplaceable

statues and buildings (Parthenon in Greece, Taj Mahal in India) react

with acid in the rain

-reaction leads to the formation of calcium salts

-the solubility of these salts in water is much greater that that of marble

in water

-the dissolution of formed calcium salts leads to roughened surfaces,

removal of material and loss of carved details from the buildings and

statues

CaCO3 (s) + 2 H+(aq) -> Ca 2+ (aq) + CO2 (g) + H2O (l)

Corrosion of metals

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Document Summary

When atmospheric carbon dioxide dissolves in water it forms carbonic acid. The production of acid rain is due to the presence of the oxides of the nonmetals nitrogen and sulfur. The acid formed dissociates partially generating small amounts of hydrogen ions. The hydrogen ions formed are responsible for the weakly acidic nature of rain. Weakly acidic nature of rain is due to dissolved co2. The acidity (a measure of hydrogen ion concentration) of a solution is conveniently described in terms of ph scale ph <7: solution is acidic ph>7: solution is basic ph=7: solution is neutral. Before working in a laboratory, you must be aware of good laboratory. Must also be aware of the health and safety aspects of the work you are planning to carry out. Should be aware of carious hazards and the location of appropriate control equipment, msdss, and personal protective equipment (safety glasses, gloves, lab coat)

Related Questions

Exp 25. pH Measurements- Buffers and Their Properties

I need help with finding kPa in the calculations part C for 1,2, and 3 Thanks!

Experiment 25 pH Measurements- Buffers and Their Properties ne of the more important propertics of an aqucous solution is its concentration of hydrogen ion. The H ion (or, more precisely, the HO ion) has a great effect on the solubility of many inorganic and organic species, on the nature of complex mctallic cations found in solutions, and on the rales of many chemical reac- tions. It is important that we know how to measure the concentration of hydrogen ion and understand its effect on solution properties. For convenience, the concentration of H' ion is frequendly expressed as the pH of the solution rather than as molarity. The pH of a solution is defined by the following equation: pH =-log where the logarithm is taken to the base 10. If [H] is I x 10-*moles per liter, the pH of the solution is, by the equation, 4. If the [H'1 is 5 x 10 M, the pH is 1.3, Basic solutions can also be described in terms of pH. In aqucous solutions the following equilibrium rela- tion will always be obeyed: In distilled water url equals [ OHÂ·], s, by Equation 2, [HÂ·l must be l x 10" M. Therefore, the pH of distilled water is 7. Solutions in which [H.] > 10é¨are sad to be acidic and will have a pH 7. A solution with a pH of 10 will have a [H"] of 1 x 10 0 M and a (OH] of I x 10M We measure the pH of a solution experimentally in two ways. In the first of these we use a chemical called an indicator, which is sensitive to pH. These substances have colors that change over a relatively short pH range (about two pH units) and can, when properly chosen, be used to delermine roughly the pH of a solu tion. Two very common indicators are litmus, usually used on paper, and phenolphthalein, the most common indicator in acid-base titrations. Litmus changes from red to blue as the pH of a solution goes from about 6 to about 8. Phenolphthalein changes from colorless to red as the pH goes from 8 to 10. A given indicator is useful for determining pH only in the region in which it changes color. Indicators are available for measure- ment of pH in all the important ranges of acidity and basicity. By matching the color of a suitable indicator in a solution of known pH with that in an unknown solution, one can determine the pH of the unknown to within about 0.3 pH units. The other method for finding pH is with a device called a pH meter. In this device two electrodes, one of which is sensitive to [H']. are immersed in a solution. The potential between the two electrodes is related to the pH. The pH meter is designed so that the scale will directly furnish the pH of the solution. A pH meter gives much more precise measurement of pH than does a typical indicator and is ordinarily used when an accurate determination of pH is needed Some acids and bases undergo substantial ionization in water, and are called strong because of their essentially complete ionization in reasonably dilute solutions. Other acids and bases, because of incomplete ionization (often far less than even 1% in 0.1 M solution), are called weak. Hydrochloric acid, HC, and sodium hydroxide, NaOH, are typical examples of a strong acid and a strong base. Acetic acid, HC,H,0, and ammonia, NH, are classic examples of a weak acid and a weak base. A weak acid will ionize according to the Law of Chemical Equilibrium: HBlaq)--H'(aq) + B-(aq)

HERE IS HOW THIS IS GOING TO WORK! IF YOU ANSWER THE QUESTIONS IWILL GIVE YOU THE 3K POINTS + MORE AFTER I REPOST IT.

2. The amount of heat involved in the synthesis of 1 mole of acompound from its elements, with all substances in their standardstates at 25*C, is called _________.

3. What is a valid unit for specific heat?

4. Use Hess's Law to find the heat of reaction in the examplebelow.

N2O4 (g) ----> 2NO2 (g)

Given that:

N2O4 (g) ----> N2 (g) + 2O2 (g) (Delta H =-9.7kJ)

2NO2 (g) ----> 2O2(g) + N2(g) ( Delta H= -67.7kJ)

5. Use Hess's Law to find the heat of reaction in the examplebelow. (Example doesn't exist btw.)

6. (Delta H) for the formation of rust (Fe2O3) is -826 kJ/mol. Howmuch energy is involved in the formation of 5 grams ofrust?

7. How many kilocalories of heat are required to raise thetemperature of 50g of aluminum from -5*C to 35*C? (Specific heat ofAluminum = 0.21 cal/g*C)

8.Calculate the (Delta H) for this reaction:

Zn(s) + Cu (2+ ion)(aq) ---> Zn(2+) + Cu(s)

(Delta H) for Cu(2+) = +64.4 kJ/Mol; (Delta H) for Zn(2+) = -152.4kJ/mol

9. The following equation shows the reaction that occurs whennitroglycerine explodes.

4C3H5O9N3 ----> 12CO2 + 6N2 + O2 +10H2O + 1725 Kcal

Is this reaction exothermic , endothermic, a combustion reaction ,or a combination reaction?

10. What does it mean for ammonia, (NH3) to have a (Delta H f) =-46 kJ/mol?

(for example: Define heat of formation. What does a negative heatof formation mean? what do the units of kJ/mol mean?)

11. What is the maximum amount of KCl that can dissolve in 500g ofwater?

(solubility of KCl is 34 g/ 100g of water at 20*C)

12.List the ways(operations) that can help make a substancedissolve faster in a solvent?

13. If a crystal added to an aqueous solution causes many particlesto come out of solution, the original solution was (saturate,unsaturated, supersaturated).

14. What is the number of moles of solute in 165 mL of a 0.82 Msolution?

15. What mass of NaCl is needed to make 350 mL of a 1.00 Msolution?

16. Colligative properties depend upon...

17. If one mole of each of these solutes in added to the sameamount of water, which solution has the highest boiling point?(glucose, aluminum sulfate, magnesium acetate, copper (I)chloride)

18. When an acid reacts with a base, what compounds areformed?

19. If the [H+] in a solution is 1x10^(-13) mol/L, what is the[OH-]?

20. If the [OH-] = 1x10^-6 mol/L, what is the pH of thesolution?

21. For a solution to be considered acidic what must be thehydrogen-ion concentration?

22. Which of the following represents a Bronsted-Lowry conjugateacid-base pair?

a) SO3(2-) and SO2 b) CO3(2-) and CO c) H3O and H2 d) NH4(+) and NH3

23. With solutions of "strong" acids and "strong" bases, the word"strong" refers to ...

24. What are the products of Al(OH)3 + H2CO3?

25.What is the concentration of hydrochloric acid if 5.0 mL of acidis neutralized by 30.0 mL of 2.00M sodium hydroxide.

26. At equilibrium, what is the rate of production of reactantscompared with the rate of production of products?

27. What is the equilibrium constant for the following reaction2SO3 ---> 2SO2 + O2

28. How does an increase in pressure affect the following reaction?2SO3 (g) --> 2SO2(g) +O2(g)

29.What stresses would shift the reaction to the right?

2SO3(g) ==> 2SO2(g) + O2(g)

30. The Keq of a reaction 4.9 x 10^(-7). Are products or reactantsfavored at equilibrium?

31. In which of these systems is the entropy decreasing?

a) air escaping from a tire b) snow melting c) a gas condensing d) salt dissolving inwater

32. If an atom is reduced in a redox reaction, what must occur toanother atom in the system?

33. Identify the oxidizing agent in the following reaction: 2Na + S---> Na2S

34. What are transferred in an oxidation -reductionreaction?

35. Give the oxidation number for each atom in KMnO4.

36. Which atom has a change in oxidation number of +4 in thefollowing reaction?

K2Cr2O7 + H2O + S ----> KOH + Cr2O3 +SO2

37. What is the oxidation number of sulfur in each of the following:

a. SO3 c.SO2(2-)

b. Na2SO4 d. S2O4 (2-)

38.Fe(3+) ----> Fe represents oxidation, reduction, orhydrolysis?

39. When the half reactions Br2+ 2e- -----> 2Br- and Na---->e- + Na(+) are combined the balanced redox equation is_____________________ ( WRITE the BALANCED REDOX eq)

40. To balance the oxygen and hydrogen for a redox reaction thattakes place in basic solution, it is necessary to use whichsubstance?

41. What particle completes this nuclear equation? 55/25 Mn + 2/1 H====> _____ +2 1/0 n

42. The half-life of tungsten-182 (182/74 W) is 1.1x10^(17) years.How long would it take for a 376.2 kg sample to decay until only123.0 grams remain?

43. After 3 days, the quantity of certain radioisotope is reducedfrom 13.6 grams to 1.9 grams. Calculate the half-life of theisotope.

44. What is the name of the compound having the formulaC8H18.

45. What is the name of the following compound:

CH3---CH2----CH---CH2--C

I \

CH3 OH

46. What is an isomer? Give an isomer of hexane (C6H14) and drawit's structure.

47. What is the name of the hydrocarbons with double covalentbonds?

48. Draw the stucture for 3-methylbutanoic acid.

49. Draw the structure for methylbenzene?

50. What is the name of the following compound:

CH3----C-----CH3

CH3

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CHEM 208 Lecture Notes - Lecture 8: Air Pollution, Bromine, Fluorine

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