O- Halogenoalkanes =)

Question 1

State the benefit to life on Earth of ozone in the upper atmosphere. (1)

Answer 1

• absorbs harmful UV radiation

Question 2

Suggest one reason why the use of CFCs was not restricted until several years after Rowland and Molina published their research. (1)

Answer 2

1. lack of evidence for ozone depletion
2. lack of alternatives to CFCs
3. commercial interest to continue to use CFCs
4. hard to obtain international agreement

Question 3

CFC-11 is a greenhouse gas that can contribute to global warming.
State and explain how CFC-11 is able to contribute to global warming. (2)

Answer 3

• absorbs infrared radiation
• the CFC molecule has polar bonds

Question 4

Why are fluoroalkanes unreactive?

Answer 4

C-F bond is very strong

Question 5

One of the reactive species formed from CCl4 acts as a catalyst in the decomposition of ozone.
Write two equations to show how this species acts as a catalyst. (2)

Answer 5

1. Cl* + O3 –> ClO* + O2
2. ClO* + O3 –> Cl* + 2O2

Question 6

Give one condition necessary for a high yield of product in elimination. (2)

Answer 6

• NaOH
• dissolved in ethanol
• high temp
• concentrated

Question 7

What is the reagent needed in elimination + what is its role? (3)

Answer 7

• ethanolic
• NaOH
• role: base/ proton acceptor

Question 8

What is the reagent needed in nucleophilic substitution + what is its role? (3)

Answer 8

• aqueous
• NaOH
• role: nucleophile/ lone pair donor

Question 9

State the role of chlorine atoms in the reaction resulting in ozone depletion. (1)

Answer 9

Catalyst

x one of the products- overall equation: 2O3–>3O2

Question 10

State the role of chlorine atoms in the reaction resulting in ozone depletion. (1)

Answer 10

Catalyst

x one of the products- overall equation: 2O3–>3O2

Question 11

Give an essential condition used to ensure the desired product is the major product in nucleophilic substitution. (1)

Answer 11

Excess NH3