IB DP Chemistry Reactivity 3.3 Electron sharing reactions IB Style Question Bank HL Paper 1

Question

Which statements about the chlorine free radical are correct?

I.     It has 18 electrons.

II.     It is an uncharged species.

III.     It is formed by homolytic fission.

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

Answer/Explanation

Markscheme

C

Examiners report

[N/A]

Question

Which of these reactions proceeds by a free radical mechanism in the presence of UV light?

A.     C6H6 + Cl2 → C6H5Cl + HCl

B.     C6H6 + 3H2 → C6H12

C.     CH2CH2 + HBr → CH3CH2Br

D.     CH3CH3 + Cl2 → CH3CH2Cl + HCl

Answer/Explanation

Markscheme

D

Examiners report

[N/A]

Question

Which is a propagation step in the free-radical substitution mechanism of ethane with chlorine?

A Cl_2 → 2 •Cl

B •C_2H_5 + Cl2 → C_2H_5Cl + •Cl

C •C_2H_5 + •Cl → C_2H_5Cl

D C_2H_6 + •Cl → C_2H_5Cl + •H

Answer/Explanation

Ans: B

Question

Which steps are involved in the free-radical mechanism of the bromination of ethane in the presence of ultraviolet radiation?

I.     \({{\text{C}}_2}{{\text{H}}_6} + {\text{Br}} \bullet  \to {{\text{C}}_2}{{\text{H}}_5} \bullet  + {\text{HBr}}\)

II.     \({{\text{C}}_2}{{\text{H}}_5} \bullet {\text{B}}{{\text{r}}_2} \to {{\text{C}}_2}{{\text{H}}_5}{\text{Br}} + {\text{Br}} \bullet \)

III.     \({{\text{C}}_2}{{\text{H}}_5} \bullet  + {\text{Br}} \bullet  \to {{\text{C}}_2}{{\text{H}}_5}{\text{Br}}\)

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

Answer/Explanation

Markscheme

D

Examiners report

[N/A]

Question

What is the mechanism for the reaction of propene with iodine in the dark?

A.     electrophilic addition

B.     electrophilic substitution

C.     free radical substitution

D.     nucleophilic substitution

Answer/Explanation

Markscheme

A

Examiners report

[N/A]
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