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

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

\[\begin{array}{|c|c|} \hline \text{Al} & 1s^2 \\ \hline \text{Ti} & 1s^2 \\ \hline \end{array}\]

(b) (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 $\text{Al}_2\text{Cl}_6$.
Draw a 'dot-and-cross' diagram to show the bonding in $\text{Al}_2\text{Cl}_6$.
Show outer electrons only.
Represent the aluminium electrons by \(\cdot\).
Represent the chlorine electrons by \(\times\).

(c) When copper is reacted directly with chlorine, only $\text{CuCl}_2$ is formed. Suggest an explanation for this observation.
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(d) 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.

(ii) Calculate the amount, in moles, of chlorine atoms that reacted.

(iii) Hence, determine the empirical formula of A.

(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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(a) (i) Write an equation, with state symbols, for the second ionisation energy of calcium.
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(ii) Use the \textit{Data Booklet} to calculate the enthalpy change that occurs when one mole of gaseous calcium ions, Ca$^{2+}$, is formed from one mole of gaseous calcium atoms. Include a sign in your answer.
enthalpy change = ................... kJ mol$^{-1}$ [3]

(b) Separate small samples of phosphorus(V) chloride and phosphorus(V) 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) phosphorus(V) chloride
observation .........................................................................................................................
approximate pH of the water ............
(ii) phosphorus(V) oxide
observation .........................................................................................................................
approximate pH of the water ............ [4]

(c) When phosphorus is heated with an excess of sulfur in an inert atmosphere, a pale yellow solid, with formula P$_4$S$_{10}$ is formed. P$_4$S$_{10}$ reacts with water to give phosphoric acid, H$_3$PO$_4$, and hydrogen sulfide, H$_2$S.
(i) Complete the equation for the reaction of P$_4$S$_{10}$ with water.
P$_4$S$_{10}$ + 16H$_2$O $\rightarrow$
(ii) Does a redox reaction occur when P$_4$S$_{10}$ reacts with water? Use the oxidation numbers of phosphorus 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, CH$_3$OH, 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.
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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.
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Methanol may be manufactured catalytically from synthesis gas, a mixture of CO, CO$_2$ and H$_2$. The CO is reacted with H$_2$ to form methanol, CH$_3$OH.

$\text{CO(g) + 2H}_2\text{(g) } \rightleftharpoons \text{ CH}_3\text{OH(g)} \quad \Delta H = -91 \text{ kJ mol}^{-1}$

(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 .........................................................................................
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   condition 2 .........................................................................................
   explanation .........................................................................................
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Carbon monoxide, which can be used to make methanol, may be formed by reacting carbon dioxide with hydrogen.

$\text{CO}_2\text{(g) + H}_2\text{(g) } \rightleftharpoons \text{ CO(g) + H}_2\text{O(g) } \quad K_c = 1.44 \text{ at 1200 K}$

(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.
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(ii) A mixture containing 0.50 mol of CO$_2$, 0.50 mol of H$_2$, 0.20 mol of CO and 0.20 mol of H$_2$O was placed in a 1.0 dm$^3$ 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.

• CO$_2$ + H$_2$ $\rightleftharpoons$ CO + H$_2$O
• initial moles 0.50    0.50    0.20    0.20

(a) Complete the following reaction scheme which starts with propanone. In each empty box, write the structural formula of the organic compound that would be formed.


(b) One of the compounds V, W, X, Y or Z is chiral.
(i) Identify this compound by its letter.
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(ii) Draw displayed formulae of the two optical isomers of this compound. Indicate with an asterisk (*) the chiral carbon atom.

(c) Write the structural formula for the organic compound formed when, under suitable conditions,
(i) compound Y reacts with compound V,

(ii) compound Y reacts with compound Z.

Ethanol, CH$_3$CHO, can be converted into compound U by the following sequence.



(a) When T is formed in step I, no other compound is produced.

Suggest a structural formula for T which contains one –OH group in its molecule. [1]

(b) Compound U has two functional groups.

You are to name one functional group present in U and show how you would identify it.
Put your answers in the table.

$$\begin{array}{|c|c|c|}\hline \text{functional group in U} & \text{reagent used in test} & \text{what would be seen} \\ \hline && \\ \hline \end{array}$$
[3]

(c) U is formed from T 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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[2]

(d) Compound U can be converted into CH$_3$CH=CHCH$_2$OH.

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 ................................................................................................................................................ [2]

U has three structural isomers.

(e) Draw the displayed formulae of two structural isomers of U that each contain the same functional groups as U. [2]

(f) When a mixture of ethanal and propanal is reacted under the same conditions as in step I above, a similar reaction occurs with the formation of compound S, C$_5$H$_{10}$O$_2$.

CH$_3$CHO + CH$_3$CH$_2$CHO $\rightarrow$ C$_5$H$_{10}$O$_2$

Suggest a structural formula for S. [1]