Exam 2

Front 1

Element with ___ atomic mass are best possible candidates for a fusion reaction.

Back 1

very low

Front 2

The number of a certain radioactive nuclide present in a sample decays from 160 to 20n in 39 minutes. What is the half-life of this radioactive species?

Back 2

28 minutes

no

13 minutes

Front 3

List the number of protons, neutrons, and nucleons (protons + neutrons), in that order, for an isotope with the symbol ^137 v55 Cs

Back 3

55, 82, 137

Front 4

List the different types of nuclear radiation (alpha, beta, gamma) in order of increasing penetrating power

Back 4

alpha < beta < gamma

Front 5

What is the mass change in grams for the reaction 2 NO2(g) ---> N2O4(g)? The enthalpy for the reaction -57.2 kJ.

Back 5

-1.91x10^-4 g

no

Front 6

follWhich of the following isotopes is the most stable?

Back 6

28 Si, 8.44 MeV/ nucleon

Front 7

Carbon dating may be used to date (once living) materials that are between 100 and 40,000 years old. The half-life of the first-order decay of carbon 14 is 5730 years. What percentage of carbon-14 remains in a sample after 1.99E4 years.

Back 7

9.01%

no

Front 8

Alpha particles are identical to

Back 8

helium nuclei

Front 9

Calculate the mass defect for the formation of phosphorus-31. The mass of a phosphorus-31 nucleus is 30.973765 amu. The masses of a proton and a neutron are 1.00728 and 1.00866 amu, respectively.

Back 9

0.27399 amu

Front 10

In the following reaction, identify X;

^252 V98 Cf (^10B, 5n) X

Back 10

^257 v103 Lr

Front 11

Consider a certain type of nucleus that has a rate constant 2.03x10^-2 min^-1. Calculate the time required for the decay to one-fourth of its initial value.

Back 11

2.03 min

Front 12

Consider a certain type of nucleus that has a half-life of 32 min. Calculate the percent of original sample of nuclides remaining after 2.1 hours have passed.

Back 12

46%

no

5.8

Front 13

Decay of ruthenium-93 by positron emission yields.

Back 13

technetium-93

Front 14

Identify the missing particle in the following equation: ^238 v92 U ---> ^4 v2 He +

Back 14

^234 v90 Th

Front 15

When atoms of beryllium-9 are bombarded with alpha particles, neutrons are produced. What new isotope is also formed?

Back 15

^12 v6 C

Front 16

If the age of the Earth is 4.5 billion years and the half-life of 40 k is 1.26 billion years, what percent of Earth's original amount of 40K remains today?

Back 16

8.4%

Front 17

Which reaction will produce an isotope of the parent nuclide?

Back 17

^210 v84 Po ---> He+

no

Br ---> n+

Front 18

Beta particles are identical to

Back 18

electrons

Front 19

Which of the following is characteristic of a nuclear reaction?

I. Electrons in atomic orbitals are involved in the breaking and forming of bonds

II. Elements are converted from one to another

III. Reaction rates are typically not affected by catalysts

IV. Atoms are rearranged by the breaking and forming of chemical bonds

Back 19

II and III

Front 20

If the mass of one neutron is 1.00866 amu, the mass of one protons is 1.00728 amu, and the mass of 14C nucleus is 13.99995 amu, calculate the binding energy for the 14 C nucleus.

Back 20

5.54x10^11kJ/mol

no

1.02 x 10 ^10

Front 21

An unstable isotope of rhenium, ^191 Re, has a half-life of 9.8 minutes and is a beta producer. What is the other product of the reaction.

Back 21

^191 Os

Front 22

In the following reaction, identify X:

^10 v5 B (X, a) ^7 v3 Li

Back 22

^0 v+1 e

no

Front 23

If a log contains 60% of the 14C present in a living tree, how long has the log been dead? The half-life of 14C is 5730 years.

Back 23

4220 years

Front 24

Elements with _____ atomic mass are best possible candidates for a fission reaction.

Back 24

very heavy

Front 25

The rate constant for the beta decay of thorium-234 is 2.881x10^-2 / day. What is the half-life of this nuclide?

Back 25

48.11 days.

no

Front 26

According to collision theory, which conditions must be met in order for molecules to react?

1. The reacting molecules must collide with sufficient energy to initiate the process of breaking and forming bonds.

2. A catalyst must be in contact with the reacting molecules for a reaction to occur.

3. The reacting molecules must collide with an orientation that can lead to rearrangement of the atoms.

Back 26

3 only

no

Front 27

Concerning the rate law, Rate=K[A]^2[B], what are appropriate units for the rate constant k?

Back 27

M^-1s^-1

no

Front 28

At 700 K, the rate constant for the following reaction is 6.2x1-^-4 min^-1. How many minutes are required for 2-% of a sample of cyclopropane to propene?

Back 28

360 min

Front 29

The elementary steps for the catalyzed decomposition of dinitrogen monoxide are shown below. Which of the following statements are correct?

1. The overall balanced reaction is N2O(g) ---> N2(g) +1/2 O2(g)

2. NO2(g) is a catalyst for the reaction

3. NO(g) is a reaction intermediate

Back 29

1, 2, and 3

no

Front 30

A reaction was experimentally determined to follow the rate law. Rate=k[A]^2 where k=0.456 s^-1M^-1. Starting with [A]0=0.500 M, how many seconds will it take for [A]t=0.250 M?

Back 30

1.14x10^-1 s

no

Front 31

Initial rate data have been determined at a certain temperature for the gaseous reaction

2NO + 2H2 ---> N2 + 2H2O

What is the value of the rate constant?

Back 31

3x10^-3

no

Front 32

The decomposition of dinitrogen pentoxide is described by the chemical equation

2 N2O5(g) ---> 4 NO2(g) + O2(g)

If the rate of appearance of O2 is equal to 2.4 mol/min at a particular moment, what is the rate of disappearance of N2O5 at that moment?

Back 32

0.600 mol/min

no

Front 33

The thermal decomposition of acetaldehyde, CH3CHO ---> CH4 +CO, is a second order reaction. The following data were obtained at 518 *C. Calculate the rate constant for the decomposition of acetaldehyde from the above data.

Back 33

6.7x10^-6 /mmHgxs

Front 34

The hydrolysis of tert-butyl chloride is given in the reaction below. If the rate law is: Rate=k[(CH3)3CCL], what is the order of the reaction with respect to water?

Back 34

first

no

Front 35

A first-order reaction is 45% complete at the end of 35 minutes. What is the length of the half-life of this reaction?

Back 35

30 min

no

Front 36

Given the initial rate data for the reaction A + B ---> C, determine the rate expression for the reaction.

Back 36

delta[C]detat = 9.98E-2 M^-2 s^-1 [A]^2[B]

Front 37

The decomposition of ozone may occur through the two-step mechanism shown:

The oxygen atom is considered to be an

Back 37

reaction intermediate

Front 38

The rate law for a reaction is found to be Rate=k[A]^2[B]. Which of the following mechanisms gives this rate law?

Back 38

III

no

Front 39

Carbon dating may be used to date material that are between 100 and 40,000 years old. The half-life of the first-order decay of carbon-14 is 5730 years. What percentage of carbon-14 remains in a sample after 1.99E4 years.

Back 39

0.910%

Front 40

For this reaction X + Y ---> Z, the reaction rate is found to depend only upon the concentration of X. A pot of 1/X versus time gives a straight line.

Back 40

rate = k[X]^2

Front 41

The following data were obtained for the reaction of NO with O2. Concentrations are in molecules/cm^3 and rates are in molecules/cm^3s. What is the rate law?

Back 41

Rate = k[NO]^2[O2]

Front 42

Chloride dioxide reacts in basic water to form chlorite and chlorate according to the following chemical equation: Under a certain set of conditions, the initial rate of disappearance of chlorine dioxide was determined to be 2.3x10^-1 M/s. What is the initial rate of appearance of chlorite ion under those same conditions?

Back 42

1.15x10^-1 M/s

Front 43

Hydrogen peroxide decomposes to water and oxygen according to the reaction below:

It he presence of large excesses of I- ion, the following set of data is obtained. What is the average rate of disappearance of H2O2(aq) in M/s in the first 45 sec of the reaction if 1 L of H2O2 reacts at 25*C and 1 atm pressure?

Back 43

1.64x10^-4 M/s

no

Front 44

Cerium(IV) ion reacts with thallium(l) ion in a one-step reaction shown below. If the rate law is rate = k[Ce^+4]^2[Tl+], what is the overall order of the reaction?

Back 44

third

Front 45

Consider the reaction:

X ---> Y + Z

Which of the following is a possible rate law?

Back 45

Rate = k[X]