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Honors 203/Chemistry 110 - Exam 3 Sample Questions

    Here is a list of information that will be given to you:

    Selected Sample Questions

  1. The petroleum refining process produces much more kerosene (hydrocarbons containing 12-18 carbons) than there is a demand for. What can be done to a kerosene mixture to turn it into something more useful?

    Cracking can be used to obtain more of the gasoline fraction. Consult text for description.

  2. Gasoline is composed of hydrocarbons containing, on average, how many carbon atoms?
    1. 1-4
    2. 5-12
    3. 12-18
    4. 18-22

    5-12 carbon atoms
  3. Describe the petroleum refining process. Include a description of what petroleum consists of, how these components are separated, and final materials are produced.
    consult the text for details (pg 192-196)

  4. Which of the following hydrocarbons would you expect to have the highest octane number? 

    

a)  H   H   H   H   H   H            b)   H   H   H   H   H
    |   |   |   |   |   |                 |   |   |   |   |
H - C - C - C - C - C - C - H         H - C - C - C - C - C - H
    |   |   |   |   |   |                 |   |   |   |   |
    H   H   H   H   H   H                 H   H   H   C   H
                                                     /|\
                                                    H H H


                                                    H H H
c)                                         d)        \|/
    H   H   H   H   H   H   H   H                 H   C   H   H
    |   |   |   |   |   |   |   |                 |   |   |   |
H - C - C - C - C - C - C - C - C - H         H - C - C - C - C - H
    |   |   |   |   |   |   |   |                 |   |   |   |
    H   H   H   H   H   H   H   H                 H   H   C   H
                                                         /|\
                                                        H H H

    (d) it is the most highly branched.

  5. The process pictured here 

    

    H   H   H   H   H   H                 H   H   H   H   H
    |   |   |   |   |   |                 |   |   |   |   |
H - C - C - C - C - C - C - H         H - C - C - C - C - C - H
    |   |   |   |   |   |                 |   |   |   |   |
    H   H   H   H   H   H                 H   H   H   C   H
                                                     /|\
                    \                   /\          H H H
                     \                  /
                     \/                /
                     _____________________
                    |                     |
                    |  Catalyst           |
                    |                     |
                     ---------------------
    is an example of:

    1. catalytic cracking
    2. catalytic reformation
    3. distillation
    4. incomplete combustion

    catalytic reformation

  6. structural isomers are two compounds which:
    1. have identical chemical formulas and properties, but different structures
    2. have identical chemical formulas and structures, but different properties
    3. have identical chemical formulas, but different properties and structures
    4. have identical properties, but different chemical formulas and structures

    have identical chemical formulas, but different properties and structures

  7. Each of the compounds or classes of compounds below are potential additives or components of gasoline. Choose one and discuss why it is (or has been) in gasoline and name one harmful effect of the compound or class of compounds.
    1. tetraethyl lead
    2. MTBE (methyltertbutyl ether)
    3. BTX compounds (benzene, toluene, xylenes and related compounds)

    consult text and notes for discussion

  8. What is reformulated gasoline?

    consult text for discussion

  9. (2 pt) An oxidizing chemical like chlorine, bleach, or ozone is usually added to water in the last stages of the municipal water treatment process. The purpose of this is to remove what contaminant?

    live bacteria

  10. True or False: water is made hard by the presence of sodium ions. (CIRCLE ONE: Do NOT write T or F)

    False: Water is made "hard" by the presence of calcium, magnesium or iron ions.

  11. Choose one of the following to answer:
    1. What are MCLG and MCLs and how are they different?
    2. How do trihalomethanes get in drinking water and what potential negative effects are there?
    3. Describe how soap removes grease from clothes.

    various answers

  12. The compound formed from sodium and oxygen is: (CHOOSE ONE)
    1. NaO
    2. Na2O
    3. NaO2
    4. Na3O2

    (b) Na2O

  13. The ionic compound consisting of Ca2+ and PO43- is: (CHOOSE ONE)
    1. CaPO4
    2. Ca2PO4
    3. Ca2(PO4)3
    4. Ca3(PO4)2

    (d) Ca3(PO4)2

  14. What is the molarity of a solution made from 0.25 moles of glucose and enough water to make 500 mL of solution? 

                      0.25 moles     
Concentration = --------------  = 0.5 M
                   0.500 L

  15. How many grams of KBr do I need to make 100 mL of a 2M solution? 

    
(2 mol/L)(0.100 L) = 0.200 moles

molar mass = 39.10 g + 79.90 g = 119.00 g 

grams needed = (0.200 moles)(119 g/mol) = 23.8 g

  16. If I mix 40 ml of isopropanol with enough water to make 250 mL of solution, what is my concentration in v/v%? 

                       40 mL     
Concentration = --------------  x 100%  =    16%
                   250 mL

  17. The concentration of H+ ion in a solution that has a pH of 3 is:
    1. 3.0 M
    2. 0.3 M
    3. 1 x 10-3 M
    4. 3 x 10-1 M

    (c) 1.0 x 10-3

  18. Lime juice has a pH of about 2. Is lime juice acidic or basic? (circle one)

    acidic

  19. Are the following substance soluble in water?
    1. NaNO3
    2. Ba(NO3)2
    3. CaCO3
    4. MgO

    (a) and (b) are soluble: Sodium (group 1A salts) are soluble, nitrates are soluble

    (c) and (d) are insoluble: Carbonates and oxides are insoluble

    (see rules discussed in class)

  20. Write the chemical equation for the dissociation of nitric acid HNO3 in water

    HNO3 (aq) + H2O (aq) --> H3O+(aq) + NO3-(aq)

  21. Write the chemical equation for the reaction of potassium hydroxide (KOH) with nitric acid (HNO3).

    KOH (aq) + HNO3 (aq) --> H2O (l) + KNO3 (aq)

  22. Calculate the hydroxide (OH-) ion concentration in a solution that has a pH of 6.8.

    [H+] = 10-pH = 10-6.8 = 1.6 x 10-7 M

    [OH-] = 1.0 x 10-14 / 1.6 x 10-7 = 6.3 x 10 -8 M

  23. Describe (in one complete sentence) 1 potential negative effect of acid rain, other than its effect on aquatic environments.

    Possible answers include: damage to statues, buildings and other objects, damage to trees and forests, health/respiratory effects on people.

  24. What is the pH of a solution with an H+ concentration of 8.14 x 10-4?

    pH = -log MH+ = 3.1

  25. Describe any one of the major sources or causes of acidic precipitation. Be specific about what the process is and what chemicals (correct names or formulas) are formed.

    Coal combustion for electric power production or iron smelting leads to the production of SO2 which is subsequently converted to H2SO4 (sulfuric acid).

    When pure metals are produced from sulfur containing ores, SO2 is released which is subsequently converted to H2SO4 (sulfuric acid).

    N2 and O2 combine in automobile engines to form NO, which is eventually converted to HNO3 (nitric acid)

  26. Besides switching to lower sulfur coal, describe one of the remaining primary methods for reducing SO_2 emissions by coal power plants and mention the method's primary disadvantage.

    Washing - The coal is crushed and "washed" with water. Heavier, sulfur containing ores sink to the bottom and can be removed. Only 1/2 of the sulfur is removed in this process.

    Scrubbing - Gases are past through a limestone (CaCO3) slurry. SO2 is removed and converted into CaSO4. This calcium sulfate solid must then be disposed of, which can be costly.

  27. Write an equation for a nuclear reaction in which Pu-239 is bombarded with an alpha particle to produce another nucleus and one neutron.

    239Pu +4 He ---> 242Pu+1 n
    942960

  28. C-14 undergoes beta decay. Write an equation for this process.
    14C ---> 14N+0e-
    67-1
  29. Bi-210 undergoes alpha decay. Write an equation for this process.
    210Bi ---> 206Tl+4He
    83812
  30. Pick ONE of the following questions to answer and answer it as completely as you can:
    1. Explain why Midwestern lakes do not suffer from acid rain in the same way that lakes in the northeast do.
    2. Explain why acid rain in Los Angeles is primarily caused by nitrogen oxides, rather than SO2.
    3. Describe how SO2 is produced from coal, which is primarily carbon.

    Consult the text for descriptions. (For Midwestern Lakes, see section 6.13, specifically pages 295-296; For LA, see section 6.8, pages 280-282; For sulfur dioxide from coal, see section 6.7, pages 279-280.)

  31. How many neutrons are represented by: 
    239
   Pu
 94


     # neutrons = mass # - atomic # = 239 - 94 = 145

  32. How many neutrons are represented by: 
    242
   Cm
 96


     # neutrons = mass # - atomic # = 242 - 96 = 146

  33. Write the nuclear reactions for the following:
    • U-238 is bombarded with a nucleus to produce Fm-249 and 5 neutrons.
    • U-235 is bombarded with N-14 to produce another nucleus and 5 neutrons.

    238U +16 O ---> 249Fm+  51 n
    9281000

    235U +14 N ---> 244Es+  51 n
    927990

  34. Describe the process of fission. Be specific - explain what particles are required and what

    A fissionable nucleus is bombarded with a neutron. The large nucleus splits into smaller nuclei (lighter elements) and releases more neutrons. In this process, mass is lost and energy is released.

  35. Use U-235 as an example and use words and diagrams to describe the process of a chain reaction.

    See diagram on page 316 (You do not need to specify all the identies and mass number and atomic numbers of the "daughter" nuclei).

  36. A sample of sodium-24 with an activity of 12 mCi is used to study the blood flow in the circulatory system. If sodium-24 has a half-life of 15 hours, what is the activity of the sodium after 2.5 days?

    2.5 days x 24 hrs/day = 60 hrs

    60 hrs x 1 half life/15 hrs = 4 half-lives

    Activity after 2.5 days = 12 mCi x (0.5)4 = 0.75 mCi

  37. Describe the problems associated with the disposal of high level nuclear waste.

    Many possible answers here. Some good things to touch on would be the technical difficulties associated with long term storage, the length of time the waste remains radioaction, the political ramifications of finding a location for nuclear waste storage, and concern about nuclear waste falling into the hands of someone wanting to make weapons.

  38. Name the four main natural sources of background radiation a person experiences on earth.

    Cosmic rays, rocks and soil, internal (within our own bodies) and radon. These make up 82% of background radiation.

  39. Name the major person-made source of background radiation a person experiences on earth.

    Medical x-rays (11%) and nuclear medicine (4%) are the two main sources.

  40. What is low-enrichment uranium and how does it differ from natural uranium.

    Natural uranium is 0.7% U-235 and 99.3% U-238. Enriched uranium has a higher U-235 content. Low enrichment corresponds to enriched uranium with a U-235 composition of less than 20%.

  41. Contrast a coal-fired power plant with a nuclear power plant in the following aspects:
    • Source of the energy
    • Process by which energy is released
    • Process by which this energy is converted into electricity
    • What the by-products of this process are and where they end up.


    		CoalNuclear
    SourceCoal, a fossil fuel U-235
    Process to release energyCombustion of coal nuclear fission
    Process to convert to electricity turbines/generator same as coal plant
    by-products large quantities of a greenhouse gas (CO2), sulfur dioxide (leading to acid rain), ash particles and other pollutants are released into the air Radioactive waste that must be stored and will remain radioactive for a long time. This is often stored in the reactors as a long term storage facility has yet to be built.

Kimberly Lawler-Sagarin