Extent and rate of reaction 3

Question 1

The reaction mechanism which predominates for a SN1/SN2 reactions depends on what?

Answer 1

• Structure of alkyl halide
• Reactivity of the nucleophile
• Concentration of the nucleophile
• Solvent of the reaction

Question 2

Define a second order reaction.

Answer 2

• Defined as the rate depending upon concentration of two reactants
• Order if a reaction is the sum of the exponents if the concentration terms in the rate law: A+B->C+D, thus, Rate=k[A][B]
• A second order reaction is also where two molecules of A combine to form B, A+A->B, thus, Rate=k[A]^2

Question 3

What does a second order require?

Answer 3

A transition state formed by both components of the reaction.

Question 4

What is the rate proportional to in a second order reaction?

Answer 4

The concentration of two components
Rate = k2[A][B]

Question 5

Simplify the second order reaction equation.

Answer 5

1/[𝐴]𝑡 = 𝑘2𝑡 + 1/[𝐴]0

Question 6

How to calculate second order half life?

Answer 6

1/𝑘2[𝐴]0 = t1/2
- Each half life is twice as long as the preceding one

Question 7

Describe a zero order reaction?

Answer 7

Proceeds at a rate independent of reactant concentration.

Question 8

Give examples of zero order kinetics.

Answer 8

• Suspensions
• Drugs in the solid phase
• Enzyme reactions - if the substrate conc. is far higher than enzyme

Question 9

State the equation for zero order reaction.

Answer 9

[A] = [A]0 - kt
- slope = -k
- Intercept = [A]0

Question 10

Give examples of zero order reactions.

Answer 10

• Hydrolysis of ampicillin suspensions

Question 11

Describe the effect of temperature on rate.

Answer 11

• Rate of reaction will depend on how often reacting molecules collide
• Collision rate depends on concentration, molecular size and speed
• Temperature affects speed
• Increases with rate
• Led to Arrhenius equation k=Ae^-Ea/RT

Question 12

State the Arrhenius equation.

Answer 12

lnk = (-Ea/R)1/T + lnA
* The larger the Ea, the smaller the rate k
* The higher T, the larger k