Question 1

Paper 2Medium6 marks

CFC-12, CF₂Cl₂, can reach the stratosphere. UV radiation can break one of its C—Cl bonds. In a simplified ozone-depletion sequence, a chlorine radical reacts with ozone to form a chlorine monoxide radical and oxygen. The chlorine monoxide radical then reacts with an oxygen radical: ClO• + O• → Cl• + O₂

(a)

Write the equation for the UV-induced breaking of one C—Cl bond in CF₂Cl₂, showing UV above the arrow. State whether this is an initiation, propagation or termination step.

[2]
(b)

Represent the bond being broken as C—Cl. Draw two single-barbed (fish-hook) arrows to show the movement of electrons during this bond breaking.

[1]
(c)

Write the balanced equation for the reaction of a chlorine radical with ozone described in the question.

[1]
(d)

Combine the reactions in the question and in part (c) to give the overall reaction. State why the chlorine radical can continue the sequence.

[2]

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