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IB Chemistry HL3.4 Electron-pair sharing reactionsQuestion Bank

3.4 Electron-pair sharing reactions

Question 1

[Maximum number: 4]

Hydrogen cyanide, HCN , is a very toxic compound.

Question 1(d)

(a)

The cyanide ion reacts with iodomethane, CH3I\mathrm{CH}_{3} \mathrm{I}.

[ 4 ]

Question 1(d)(i)

(i)

Draw the structural formula of the organic product.

[ 1 ]

Question 1(d)(ii)

(ii)

Predict, giving a reason, whether this reaction will occur by an SN1\mathrm{S}_{\mathrm{N}} 1 or SN2\mathrm{S}_{\mathrm{N}} 2 mechanism.

[ 1 ]

Question 1(d)(iii)

(iii)

Explain how you might experimentally conclude whether the mechanism of this reaction is SN1\mathrm{S}_{\mathrm{N}} 1 or SN2\mathrm{S}_{\mathrm{N}} 2.

[ 2 ]

Question 1

[Maximum number: 2]

Alkanes are commonly occurring organic compounds.

Question 1(c)

(a)

Chloroethane can be converted to ethanol. Identify the reagent and conditions necessary for this reaction to occur.

Reagent:
Conditions:

[ 2 ]

Question 1

[Maximum number: 2]

Urea, (H2 N)2CO\left(\mathrm{H}_{2} \mathrm{~N}\right)_{2} \mathrm{CO}, is excreted by mammals and can be used as a fertilizer.

Question 1(h)

(a)

Describe the bond formation when urea acts as a ligand in a transition metal complex ion.

[ 2 ]

Question 1

[Maximum number: 3]

Chlorine undergoes many reactions.

Question 1(d)

Question 1(d)(iii)

(a)
(i)

Explain the mechanism of the reaction between chloroethane and aqueous sodium hydroxide, NaOH(aq), using curly arrows to represent the movement of electron pairs.

[ 3 ]

Question 8

[Maximum number: 1]

Which statements are correct about the complex [Cu(NH3)2Cl2]\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\right] ?

I. Oxidation state of copper is +2 .
II. Ammonia is a ligand.
III. Chloride ions act as Lewis acids.

A

I and II only

B

I and III only

C

II and III only

D

I, II and III

Question 8

[Maximum number: 1]

Which species cannot act as a ligand?

A

NH4+\mathrm{NH}_{4}{ }^{+}

B

H2O\mathrm{H}_{2} \mathrm{O}

C

Cl−\mathrm{Cl}^{-}

D

OH−\mathrm{OH}^{-}

Question 8

[Maximum number: 1]

Cobalt forms the complex [Co(NH3)5Cl]2+\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right]^{2+}. Which statements are correct for this complex?

I. The cobalt ion acts as a Lewis acid.
II. The cobalt ion has an oxidation number of + II.
III. There are 90∘90^{\circ} bond angles between the cobalt ion and the ligands.

A

I and II only

B

I and III only

C

II and III only

D

I, II and III

Question 2

[Maximum number: 5]

Alkenes are useful in industry.

Question 2(b)

(a)

But-1-ene reacts with HBr to produce two structural isomers of bromobutane.

[ 5 ]

Question 2(b)(i)

(i)

Explain which of the two structural isomers is the major product.

[ 2 ]

Question 2(b)(ii)

(ii)

Explain the mechanism for the formation of the major product using curly arrows to represent the movement of electron pairs.

[ 3 ]

Question 3

[Maximum number: 1]

Ammonia is produced industrially using the reversible reaction.

N2( g)+3H2( g)⇌2NH3( g)\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NH}_{3}(\mathrm{~g})

Question 3(b)

Question 3(b)(i)

(a)
(i)

Outline how ammonia acts as a Lewis base when it forms the complex ion

[Cu(NH3)4(H2O)2]2+(aq).\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right]^{2+}(\mathrm{aq}) .
[ 1 ]

Question 2

Question 2(b)

(a)

Cu2+(aq)\mathrm{Cu}^{2+}(\mathrm{aq}) reacts with ammonia to form the complex ion [Cu(NH3)4]2+\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}.

Explain this reaction in terms of acid-base theory, and outline the bonding in the complex formed between Cu2+\mathrm{Cu}^{2+} and NH3\mathrm{NH}_{3}.

[ 3 ]
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