[Maximum number: 3]

The elements in Group 17 are known as the halogens.

(a)

Sodium chlorate(I), NaClO, oxidises dilute hydrochloric acid to form three products. The products which contain chlorine have chlorine species with oxidation number -1 or 0.

No other species changes its oxidation number during the reaction.
Use this information to complete the ionic equation.

\ldots \ldots . . \mathrm{ClO} \mathrm{O}^{-}+\ldots \ldots . \mathrm{HCl} \rightarrow \ldots \ldots \ldots . . .+\ldots \ldots \ldots . . .+\ldots \ldots . \ldots . .

[ 3 ]

[Maximum number: 1]

Hydrazine, $\mathrm{N}_{2} \mathrm{H}_{4}$ , can be used as a rocket fuel and is stored as a liquid. It reacts exothermically with oxygen to give only gaseous products.

The enthalpy change of a reaction such as that between hydrazine and oxygen may be calculated by using standard enthalpy changes of formation.

(a)

Deduce the oxidation state of nitrogen in hydrazine.

[ 1 ]

[Maximum number: 12]

Ethanoic acid can be reacted with alcohols to form esters, an equilibrium mixture being formed.

\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}+\mathrm{ROH} \rightleftharpoons \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{R}+\mathrm{H}_{2} \mathrm{O}

The reaction is usually carried out in the presence of an acid catalyst.

(a)

(i)

What amount, in moles, of this NaOH reacted with the hydrogen chloride?

(a)

A compound of barium, A, is used in fireworks as an oxidising agent and to produce a green colour.

[ 1 ]

(i)

Explain, in terms of electron transfer, what is meant by the term oxidising agent.

[ 1 ]

[Maximum number: 2]

Copper is used in electrical equipment. It has a melting point of $1085^{\circ} \mathrm{C}$ .

(a)

When KI(aq) is added to $\mathrm{CuSO}_{4}(\mathrm{aq})$ the blue-coloured solution turns brown and a white precipitate of CuI(s) is seen.

The reaction between copper ions and iodide forms only two products.

[ 2 ]

(i)

Complete the equation for this reaction.

\ldots \ldots \ldots . . \mathrm{Cu}^{2+}+\ldots \ldots \ldots . . \mathrm{I}^{-} \rightarrow \ldots \ldots \ldots . . \mathrm{CuI}+\ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots . . . .

[ 1 ]

(ii)

Identify the oxidising agent in this reaction. Explain your answer in terms of electron transfer.

[ 1 ]

(a)

When magnesium is heated in air, magnesium oxide, MgO , is the major product. Smaller amounts of magnesium nitride, $\mathrm{Mg}_{3} \mathrm{~N}_{2}$ , are also made.

[ 2 ]

(i)

Calculate the oxidation number for magnesium and for the nitrogen species in $\mathrm{Mg}_{3} \mathrm{~N}_{2}$ to complete Table 1.1.

Table 1.1

[ 1 ]

(ii)

Identify the type of reaction which takes place between magnesium and nitrogen. Explain your answer.

[ 1 ]

(a)

Magnesium can be produced by electrolysis of magnesium chloride in a molten mixture of salts.

[ 2 ]

(i)

Give equations for the anode and cathode reactions during the electrolysis of molten magnesium chloride, $\mathrm{MgCl}_{2}$ .
anode
cathode

The electrolysis is carried out under an atmosphere of hydrogen chloride gas to convert any magnesium oxide impurity into magnesium chloride.

[ 2 ]

[Maximum number: 3]

An experiment was carried out to determine the percentage of iron in a sample of iron wire.

(a)

A3.35 g piece of the wire was reacted with dilute sulfuric acid, in the absence of air, so that all of the iron atoms were converted to iron(II) ions. The resulting solution was made up to $250 \mathrm{~cm}^{3}$ .

[ 3 ]

(i)

Write a balanced equation for the reaction between the iron in the wire and the sulfuric acid.

A $25.0 \mathrm{~cm}^{3}$ sample of this solution was acidified and titrated with $0.0250 \mathrm{moldm}^{-3}$ potassium dichromate(VI). $32.0 \mathrm{~cm}^{3}$ of the potassium dichromate(VI) solution was required for complete reaction with the iron(II) ions in the sample.

The relevant half-equations are shown.

\begin{gathered} \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-} \rightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_{2} \mathrm{O} \\ \mathrm{Fe}^{2+} \rightarrow \mathrm{Fe}^{3+}+\mathrm{e}^{-} \end{gathered}

[ 1 ]

(ii)

Use the half-equations to write an equation for the reaction between the iron(II) ions and the acidified dichromate(VI) ions.

[ 1 ]

(iii)

Calculate the amount, in moles, of iron(II) ions in the $25.0 \mathrm{~cm}^{3}$ sample of solution.

amount =mol [1]

[ 1 ]

[Maximum number: 3]

Hydrogen iodide, HI, is a colourless gas at room temperature.

(a)

HI reacts with oxygen to form iodine and water.

[ 3 ]

(i)

Construct an equation for the reaction of HI with oxygen.

[ 1 ]

(ii)

Explain, with reference to oxidation numbers, why this reaction is a redox reaction.

[ 2 ]

(a)

Chlorine can be prepared using the following reaction.

\mathrm{MnO}_{2}(\mathrm{~s})+4 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{MnCl}_{2}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{Cl}_{2}(\mathrm{~g})

[ 2 ]

(i)

Explain why $\mathrm{MnO}_{2}(\mathrm{~s})$ is described as an oxidising agent in this reaction.

Refer to oxidation numbers in your answer.

[ 1 ]

(ii)

State what you would observe during this reaction.

[ 1 ]

Question 1

Question 1(f)

Question 1

Question 1(d)

Question 1

Question 1(b)

Question 1(b)(ii)

Question 1

Question 1(c)

Question 1(c)(i)

Question 1

Question 1(d)

Question 1(d)(i)

Question 1(d)(ii)

Question 1

Question 1(b)

Question 1(b)(i)

Question 1(b)(ii)

Question 1

Question 1(c)

Question 1(c)(i)

Question 1

Question 1(a)

Question 1(a)(i)

Question 1(a)(ii)

Question 1(a)(iv)

Question 1

Question 1(d)

Question 1(d)(i)

Question 1(d)(ii)

Question 1

Question 1(a)

Question 1(a)(i)

Question 1(a)(ii)