AP Nuclear and Organic Review

AP Nuclear and Organic Review with Answers

Multiple Choice:

1. Types of hybridization exhibited by the C atoms in propene, CH3CHCH2, include which of the following?

I. sp II. sp2 III. sp3

(A) I only (B) III only

(E) I, II, and III

2. O

CH3—C—CH2—CH3

The organic compound represented above is an example of

(A) an organic acid (B) an alcohol

(E) a ketone

3. If 87.5 percent of a sample of pure 131I decays in 24 days, what is the half-life of 131I?

(A) 6 days (B) 8 days (C) 12 days

(D) 14 days (E) 21 days

The graph above shows the results of a study of the reaction of X with a large excess of Y to yield Z. The concentrations of X and Y were measured over a period of time. According to the results, which of the following can be concluded about the rate law for the reaction under the conditions studied?

(A) It is zero order in [X].

(B) It is first order in [X].

(D) It is first order in [Y].

(E) The overall order of the reaction is 2.

5. CH3CH2OH boils at 78_C and CH3OCH3 boils at –24_C, although both compounds have the same composition. This difference in boiling points may be attributed to a difference in

(A) molecular mass (B) density

(E) heat of combustion

6. X. CH3–CH2–CH2–CH2–CH3

Y. CH3–CH2–CH2–CH2–OH

Z. HO–CH2–CH2–CH2–OH

Based on concepts of polarity and hydrogen bonding, which of the following sequences correctly lists the compounds above in the order of their increasing solubility in water?

(A) Z < Y < X (B) Y < Z < X

(E) X < Y < Z

7. Which of the following pairs of compounds are isomers?

(A) CH3-CH2-CH2-CH3 and CH3-H-CH3

CH3

(B) CH3-H–CH3 and CH-=CH2

CH3 CH3

(D) CH3-OH and CH3-CH2-OH

(E) CH4 and CH2=CH2

8. The isomerization of cyclopropane to propylene is a first–order process with a half–life of 19 minutes at 500_C. The time it takes for the partial pressure of cyclopropane to decrease from 1.0 atmosphere to 0.125 atmosphere at 500_C is closest to

(A) 38 minutes (B) 57 minutes

(E) 190 minutes

9. For the types of radiation given, which of the following is the correct order of increasing ability to penetrate a piece of lead?

a. Alpha particles < gamma rays < beta particles

b. Alpha particles < beta particles < gamma rays

c. Beta particles < alpha particles < gamma rays

d. Beta particles < gamma rays < alpha particles

e. Gamma rays < alpha particles < beta particles

10. The structural isomers C2H5OH and CH3OCH3 would be expected to have the same values for which of the following? (Assume ideal behavior.)

a. Gaseous densities at the same temperature and pressure

b. Vapor pressures at the same temperature

c. Boiling points

d. Melting points

e. Heats of vaporization

11. ® 2 n + + _?

What is the missing product in the nuclear reaction represented above?

a. c. e.

b. d.

12. Which of the following does NOT behave as an electrolyte when it is dissolved in water?

a. CH3OH c. NH4Br e. Sodium acetate, CH3COONa

b. K2CO3 d. HI

13. Which of the following represents a pair of isotopes?

Atomic Mass

Number Number

(A) I. 6 14

II. 7 14

(B) I. 6 7

II. 14 14

II. 14 28

(D) I. 7 13

II. 7 14

(E) I. 8 10

II. 16 20

14. When decays, the emission consists consecutively of an a particle, then two b particles, and finally another a particle. The resulting stable nucleus is

(A) (B)210 82 Pb (C) (D)21083 Bi (E)

15. The radioactive decay of to occurs by the process of

(A) beta particle emission (D) electron capture

(B) alpha particle emission (E) neutron capture

16. The alkenes are compounds of carbon and hydrogen with the general formula CnH2n. If 0.561 gram of any alkene is burned in excess oxygen, what number of moles of H2O is formed?

(A) 0.0400 mole (C) 0.0800 mole (E) 0.800 mole

(B) 0.0600 mole (D) 0.400 mole

17. A 27.0–gram sample of an unknown hydrocarbon was burned in excess oxygen to form 88.0 grams of carbon dioxide and 27.0 grams of water. What is a possible molecular formula of the hydrocarbon?

(A) CH4 (C) C4H3 (E) C4H10

(B) C2H2 (D) C4H6

MC Answers: 1. D 2. E 3. B 4. B 5. D 6. E 7. A 8. B 9. B 10. A 11. B 12. A 13. D 14. C 15. A 16. A 17. D

II Free Response:

1997 D

Answer each of the following questions regarding radioactivity.

(a) Write the nuclear equation for decay ofby alpha emission.

(b) Account for the fact that the total mass of the products of the reaction in part (a) is slightly less than that of the original .

(c) Describe how a, b, and g rays each behave when they pass through an electric field. Use the diagram below to illustrate your answer.

(d) Why is it not possible to eliminate the hazard of nuclear waste by the process of incineration?

Answer:

(a) ® +

Due to a printing error, the student’s answer booklet had the Pu-239 isotope. Therefore, the following is a valid response.

® +

(b) This mass defect has been converted into energy. DE = Dmc2

(c) An alpha particle, a or He nuclei, has a 2+ charge and would be attracted to the (-) side of the electric field. A beta particle, b, or electron, has a single negative charge and is attracted to the positive side of the electric field, but since it is much lighter and faster than an alpha it would not be as strongly deflected. Gamma, g, rays are not charged and, therefore, not deflected by the electric field.

(d) The half-life of a radionuclide is independent of its environment. Incineration will neither accelerate its decay nor render it non-radioactive. Half-life is a function of its nucleus, incineration is a function of its electrons.

2007 part A, form B, question #2 (repeated in the atomic theory section)

Answer the following problems about gases.

(a) The average atomic mass of naturally occurring neon is 20.18 amu. There are two common isotopes of naturally occurring neon as indicated in the table below.

Isotope / Mass (amu)
Ne-20 / 19.99
Ne-22 / 21.99

(i) Using the information above, calculate the percent abundance of each isotope.

(ii) Calculate the number of Ne-22 atoms in a 12.55 g sample of naturally occurring neon.

(b) A major line in the emission spectrum of neon corresponds to a frequency of 4.34´1014 s-1. Calculate the wavelength, in nanometers, of light that corresponds to this line.

(c) In the upper atmosphere, ozone molecules decompose as they absorb ultraviolet (UV) radiation, as shown by the equation below. Ozone serves to block harmful ultraviolet radiation that comes from the Sun.

O3(g) O2(g) + O(g)

A molecule of O3(g) absorbs a photon with a frequency of 1.00´1015 s-1.

(i) How much energy, in joules, does the O3(g) molecule absorb per photon?

(ii) The minimum energy needed to break an oxygen-oxygen bond in ozone is 387 kJ mol-1. Does a photon with a frequency of 1.00´1015 s-1 have enough energy to break this bond? Support your answer with a calculation.

Answer:

(a) (i) let X = decimal percentage of Ne-20, then (1-X) = decimal percentage of Ne-22

19.99X + 21.99(1-X) = 20.18; X = 0.905 or 90.50% Ne-20 and 9.500% Ne-22

(ii) (12.55 g)(9.5%) ´= 3.557´1022 atoms

(b) c = ln; l = = 690 nm

(ii) 6.63´10-19 J ´ = 399 kJ; this is more than 387 kJ, so there is enough energy to break the bond.

1998 D

Answer each of the following using appropriate chemical principles.

(c) Dimethyl ether, H3C-O-CH3, is not very soluble in water. Draw a structural isomer of dimethyl ether that is much more soluble in water and explain the basis of its increased water solubility.

In each case, justify your choice.

Answer

(c) The O-H bond in ethyl alcohol is very polar and will allow the molecule to be attracted to and dissolve in the polar water.

2002 B

Consider the hydrocarbon pentane, C5H12 (molar mass 72.15 g).

(a) Write the balanced equation for the combustion of pentane to yield carbon dioxide and water.

(b) What volume of dry carbon dioxide, measured at 25˚C and 785 mm Hg, will result from the complete combustion of 2.50 g of pentane?

(c) The complete combustion of 5.00 g of pentane releases 243 kJ of heat. On the basis of this information, calculate the value of ∆H for the complete combustion of one mole of pentane.

(d) Under identical conditions, a sample of an unknown gas effuses into a vacuum at twice the rate that a sample of pentane gas effuses. Calculate the molar mass of the unknown gas.

(e) The structural formula of one isomer of pentane is shown below. Draw the structural formulas for the other two isomers of pentane. Be sure to include all atoms of hydrogen and carbon in your structures.

Answer:

(a) C5H12 + 8 O2 ® 5 CO2 + 6 H2O

(b) 2.50 g C5H12 ´ ´ = 0.173 mol CO2

V = = =

4.10 L

(d) = ; = ; M2 = 18.0

(e)

2003 D (repeated in bonding)

Compound Name / Compound Formula / ∆H˚vap
(kJ mol-1)
Propane / CH3CH2CH3 / 19.0
Propanone / CH3COCH3 / 32.0
1-propanol / CH3CH2CH2OH / 47.3

Using the information in the table above, answer the following questions about organic compounds.

(a) For propanone,

(i) draw the complete structural formula (showing all atoms and bonds);

(ii) predict the approximate carbon-to-carbon-to-carbon bond angle.

(b) For each pair of compounds below, explain why they do not have the same value for their standard heat of vaporization, ∆H˚vap. (You must include specific information about both compounds in each pair.)

(i) Propane and propanone

(ii) Propanone and 1-propanol

(d) Given the structural formula for propyne below,

| ¯

H—C—CºC—H

(i) indicate the hybridization of the carbon atom indicated by the arrow in the structure above;

(ii) indicate the total number of sigma (s) bands and the total number of pi (π) bonds in the molecule

Answer:

(a) (i)

(ii) 120˚

(b) (i) propane, 26 electrons, molar mass = 44

propanone, 32 electrons, molar mass = 58

higher # electrons means larger van der Waal forces, larger molar mass means a slower molecule, the oxygen creates a polar molecule and dipol–dipole interactions

(ii) 1-propanol has an –OH which creates a site for hydrogen bonding with other –OH on adjacent molecules increasing intermolecular forces that must be overcome in order to vaporize the liquid.

(c)

(d) (i) sp

(ii) 6 sigma, 2 pi