IB Chemistry HL R3.3 Electron sharing reactions questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Question 1

Paper 2Easy6 marks

Ethane reacts with bromine under ultraviolet light. Bromoethane is one product, and the reaction proceeds by a radical chain mechanism.

(a)

Write the two propagation equations for the reaction of ethane with bromine.

[2]
(b)

Write a termination equation involving two ethyl radicals.

[1]
(c)

State one reason why a mixture of organic products can form.

[1]
(d)

State two features of alkanes that contribute to their low reactivity.

[2]

Question 2

Paper 2Medium6 marks

Chlorine reacts with propane when irradiated with ultraviolet (UV) light. Figure 1 shows the displayed structural formula of propane.

CCCHHHHHHHH
(a)

Determine the number of different monochlorinated structural isomers that can form from propane.

[1]
(b)

Write the equation for the initiation step, using single-barbed arrows to show the movement of electrons.

[2]
(c)

For the formation of 2-chloropropane:

(i)

Write the first propagation equation, in which a hydrogen atom is transferred from propane to a chlorine radical.

[1]
(ii)

Using the propan-2-yl radical, CH₃CH•CH₃, write the second propagation equation.

[1]
(d)

Write one equation for a termination step in this chain reaction.

[1]

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