AS & A Level Chemistry - 9701 Paper 2 2009 Summer Zone 1

Copper and titanium are each used with aluminium to make alloys which are light, strong and resistant to corrosion. Aluminium, $Al$, is in the third period of the Periodic Table; copper and titanium are both transition elements.

(a) Complete the electronic configuration of aluminium and of titanium, proton number 22.

$Al$	1s2
$Ti$	1s2

(b) Aluminium reacts with chlorine.
(i) Outline how, starting from aluminium powder, this reaction could be carried out in a school or college laboratory to give a small sample of aluminium chloride. A diagram is not necessary.
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(ii) Describe what you would see during this reaction.
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(iii) At low temperatures, aluminium chloride vapour has the formula $Al_2Cl_6$. Draw a ‘dot-and-cross’ diagram to show the bonding in $Al_2Cl_6$. Show outer electrons only. Represent the aluminium electrons by •. Represent the chlorine electrons by x.

Copper forms two chlorides, $CuCl$ and $CuCl_2$.
(c) When copper is reacted directly with chlorine, only $CuCl_2$ is formed. Suggest an explanation for this observation.
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(d) Titanium also reacts with chlorine.
When an excess of chlorine was reacted with 0.72 g of titanium, 2.85 g of a chloride $A$ was formed.

(i) Calculate the amount, in moles, of titanium used.
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(ii) Calculate the amount, in moles, of chlorine atoms that reacted.
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(iii) Hence, determine the empirical formula of $A$.
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(iv) Construct a balanced equation for the reaction between titanium and chlorine.
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(e) At room temperature, the chloride of titanium, $A$, is a liquid which does not conduct electricity.
What does this information suggest about the bonding and structure in $A$?
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Magnesium will react on heating with chlorine, or oxygen, or nitrogen to give the chloride, or oxide, or nitride respectively. Each of these compounds is ionic and in them magnesium has the same +2 oxidation state.

(a) (i) Write an equation, with state symbols, for the second ionisation energy of magnesium.
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(ii) Use the Data Booklet to calculate the enthalpy change that occurs when one mole of gaseous magnesium ions, Mg²⁺, is formed from one mole of gaseous magnesium atoms.
Include a sign in your answer.

enthalpy change = ……………… kJ mol^–1

(b) Separate samples of magnesium chloride and magnesium oxide are shaken with water. In each case, describe what you would see when this is done, and state the approximate pH of the water after the solid has been shaken with it.

(i) magnesium chloride
observation .......................................................................................................................
approximate pH of the water …………………

(ii) magnesium oxide
observation .......................................................................................................................
approximate pH of the water …………………

(c) Magnesium burns in nitrogen to give magnesium nitride, a yellow solid which has the formula Mg₃N₂.

Magnesium nitride reacts with water to give ammonia and magnesium hydroxide.

(i) Construct an equation for the reaction of magnesium nitride with water.
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(ii) Does a redox reaction occur when magnesium nitride reacts with water?
Use the oxidation numbers of nitrogen to explain your answer.
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Concern over the ever-increasing use of fossil fuels has led to many suggestions for alternative sources of energy. One of these, suggested by Professor George Olah, winner of a Nobel Prize in chemistry, is to use methanol, CH₃OH, which can be obtained in a number of different ways. Methanol could be used instead of petrol in a conventional internal combustion engine or used to produce electricity in a fuel cell.
(a) Construct a balanced equation for the complete combustion of methanol. ...............................................................................................................................................................................

When hydrocarbon fuels are completely burned in an internal combustion engine, several toxic pollutants may be formed.
(b) State two toxic pollutants that can be produced after complete combustion of a hydrocarbon fuel in an internal combustion engine. ...............................................................................................................................................................................

Methanol may be manufactured catalytically from synthesis gas, a mixture of CO, CO₂ and H₂. The CO is reacted with H₂ to form methanol, CH₃OH.
$$CO(g) + 2H₂(g) \rightleftharpoons CH₃OH(g) \quad \Delta H = -91 \text{ kJ mol}^{-1}$$
(c) From your understanding of Le Chatelier's principle, state two conditions that could be used in order to produce a high yield of methanol.
In each case, explain why the yield would increase.
condition 1 .........................................................................................................................................................
explanation .................................................................................................................................
condition 2 .........................................................................................................................................................
explanation .................................................................................................................................

Carbon monoxide, which can be used to make methanol, may be formed by reacting carbon dioxide with hydrogen.
$$CO₂(g) + H₂(g) \rightleftharpoons CO(g) + H₂O(g) \qquad K_c = 1.44 \text{ at 1200 K}$$
(d) (i) It has been suggested that, on a large scale, this reaction could be helpful to the environment.
Explain, with reasons, why this would be the case. .....................................................................................................................
(ii) A mixture containing 0.50 mol of CO₂, 0.50 mol of H₂, 0.20 mol of CO and 0.20 mol of H₂O was placed in a 1.0 dm³ flask and allowed to come to equilibrium at 1200 K.
Calculate the amount, in moles, of each substance present in the equilibrium mixture at 1200 K.
$$\begin{array}{cccc} \text{CO₂} & + & \text{H₂} & \rightleftharpoons & \text{CO} & + & \text{H₂O} \\ \text{initial moles} & 0.50 & 0.50 & & 0.20 & & 0.20 \end{array}$$

(a) Complete the following reaction scheme which starts with ethanol.

In each empty box, write the structural formula of the organic compound that would be formed.



(b) Write the structural formula for the organic compound formed when, under suitable conditions,

(i) compound C reacts with compound D,

(ii) compound C reacts with compound E.

(c) Compound B is chiral. Draw displayed formulae of the two optical isomers of compound B, indicating with an asterisk (*) the chiral carbon atom.

(a) When F is formed in step I no other compound is produced. Suggest a structural formula for F, which contains one –OH group.

(b) Compound G has two functional groups.

Name one functional group present in G and show how you would identify it. Put your answers in the table.

| functional group in G | reagent used in test | what would be seen |
|----------------------|--------------------|-------------------|

(c) G is formed from F in step II. Use your answers to (a) and (b) to suggest

(i) what type of reaction occurs in step II,
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(ii) a reagent for step II.
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(d) The production of MIBK from G in step III involves the hydrogenation of the >C=C< group and is carried out catalytically. A mixture of compounds is formed because the >C=O group is also reduced.

What reagent(s) and solvent are normally used in a laboratory to reduce a >C=O group without reducing a >C=C< group present in the same molecule?

reagent(s) ..........................................................

solvent .............................................................

(e) Draw the displayed formulae of a pair of structural isomers of G which contain the CH$_3$CO– group and which exhibit cis-trans isomerism.

Label each structure cis or trans and give your reasoning.