Consider the three-step mechanism for the reaction of A through intermediates B and C to produce D shown below.
A → B E_a = 15 kcal/mol, ΔH° = 13 kcal/mol
B → C E_a = 10 kcal/mol, ΔH° = -6 kcal/mol
C → D E_a = 2 kcal/mol, ΔH° = -20 kcal/mol
Which of the three steps is rate-limiting?

A) The reaction of A to B.
B) The reaction of B to C.
C) The reaction of C to D.
D) All three steps occur at the same rate; there is no rate-limiting step.
E) The most exothermic step is rate-limiting.

What is the heat of fusion?

A) The heat needed to melt a solid completely.
B) The heat required to join two metals.
C) The heat needed to separate two metals.
D) The heat required to melt a fuse.

Why was soil in the loop of a shovel able to link Tommy Karate Pitera to a crime site?

How does the oxidation number of H change in the following reaction: CH₄ + 2 O₂ → CO₂ + 2 H₂O?

A) It goes from -1 to +1.
B) It goes from -2 to +2.
C) It does not change.
D) There is not enough information to tell.

Conversion of aldehydes and ketones to imines is an acid-catalyzed process. Explain why this conversion is actually hindered by the presence of too much acid.

What IR absorption is characteristic of the O-H stretch in alcohols?

A) 4000 cm^-1
B) 3300 cm^-1
C) 2950 cm^-1
D) 2250 cm^-1
E) 1710 cm^-1

The aldol condensation is ________.

A) an irreversible reaction
B) an equilibrium reaction
C) a tautomerization
D) an isomerization
E) a type of esterification

Through what sequence of steps can toluene be converted into

Of the four natural nucleic acids, what does "T" stand for?

A) Adenine
B) Cytosine
C) Thymine
D) Guanine

What kind of compound is AgCl in water?

A) insoluble
B) soluble
C) dissolvable
D) not enough information to tell