Chemistry S2

Question 1

In free radical reactions, the step which involves a net increase in the number of free radicals is known as:

A. Initiation
B. Propagation
C. Termination
D. None of the above

Answer 1

A. Initiation

Question 2

In free radical reactions, the step which involves a net decrease in the number of free radicals is known as:

A. Initiation
B. Propagation
C. Termination
D. None of the above

Answer 2

C. Termination

Question 3

In free radical reactions, the step which involves no change in the number of free radicals is known as:

A. Initiation
B. Propagation
C. Termination
D. None of the above

Answer 3

B. Propagation

Question 4

If deltaH is negative and deltaS is negative, the reaction is:

A. Spontaneous at high temperatures
B. Spontaneous at low temperatures
C. Always spontaneous
D. Never spontaneous

Answer 4

B. Spontaneous at low temperatures

(deltaG can be positive or negative, will only be negative at low temperatures)

deltaG = deltaH - TdeltaS

Question 5

If deltaH is negative and deltaS is positive, the reaction is:

A. Spontaneous at high temperatures
B. Spontaneous at low temperatures
C. Always spontaneous
D. Never spontaneous

Answer 5

C. Always spontaneous

(deltaG will always be negative)

deltaG = deltaH - TdeltaS

Question 6

If deltaH is positive and deltaS is negative, the reaction is:

A. Spontaneous at high temperatures
B. Spontaneous at low temperatures
C. Always spontaneous
D. Never spontaneous

Answer 6

D. Never spontaneous

(deltaG will always be positive)

deltaG = deltaH - TdeltaS

Question 7

If deltaH is positive and deltaS is positive, the reaction is:

A. Spontaneous at high temperatures
B. Spontaneous at low temperatures
C. Always spontaneous
D. Never spontaneous

Answer 7

A. Spontaneous at high temperatures

(deltaG will only be negative at high temps)

deltaG = deltaH - TdeltaS

Question 8

How do you work out the rate constant using the half life of a first order reaction?

Answer 8

k = In(2)/(half life)

Question 9

What formula is used to calculate the enthalpy of a reaction in a calorimeter?

Answer 9

deltaH = mCpdeltaT

Question 10

When bonds are broken is energy released from or added to the system?

Answer 10

When bonds are BROKEN, energy is ADDED to the system (i.e. bond breaking is ENDOTHERMIC, deltaH is positive)

Question 11

When bonds are made is energy released from or added to the system?

Answer 11

When bonds are MADE, energy is REMOVED from the system (i.e. bond formation is EXOTHERMIC, deltaH is negative)

Question 12

What is formed when a primary amine is oxidised?

Answer 12

A nitrile

Question 13

What is esterification?

Answer 13

Combining an alcohol and a carboxylic acid to form an ester

Question 14

What is formed when a secondary amine is oxidised?

Answer 14

An amide

Question 15

Grinard reagents must be kept dry, why is this?

Answer 15

They react with water to form alkanes

Question 16

How do grinard reagents react with a carbonyl compound?

Answer 16

They add across the C=O bond, with the carbon chain adding to the carbon centre, and the rest of the reagent adding to the other side of the oxygen atom. In the presence of dilute acid, they will continue to react and form an alcohol.