AS & A Level Chemistry - 9701 Paper 2 2013 Winter Zone 3

Ammonia, $NH_3$, and methane, $CH_4$, are the hydrides of elements which are next to one another in the Periodic Table.

(a) In the boxes below, draw the ‘dot-and-cross’ diagram of a molecule of each of these compounds. Show outer electrons only. State the shape of each molecule.



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(b) Ammonia is polar whereas methane is non-polar. The physical properties of the two compounds are different.

(i) Explain, using ammonia as the example, the meaning of the term \textit{bond polarity}.
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(ii) Explain why the ammonia molecule is polar.
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(iii) State \textit{one} physical property of ammonia which is caused by its polarity.
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(c) When ammonia gas is mixed with hydrogen chloride, white, solid ammonium chloride is formed.

State \textit{each type} of bond that is present in one formula unit of ammonium chloride and how many of each type are present. You may draw diagrams.
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Petrol and diesel fuel are both used in internal combustion engines. Petrol may be regarded as having the formula $C_9H_{20}$ and diesel fuel as having the formula $C_{14}H_{30}$.
(a) (i) To which class of compounds do these two hydrocarbons belong?
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(ii) Write a balanced equation for the complete combustion of petrol.
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(b) When petrol or diesel fuel are used in internal combustion engines, several different products of the incomplete combustion of the fuel may be formed.
(i) Name two of these products that do not contain hydrogen.
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(ii) Choose one of these and state a hazard it causes.
product ............................................................................................................
hazard ..............................................................................................................
(iii) Write a balanced equation for the formation of one of the products in (i) from diesel fuel.
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(c) Define the term standard enthalpy change of combustion.
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(d) A 1.00 $cm^3$ sample of $C_{14}H_{30}$ was completely burnt in air. The heat produced raised the temperature of 250 g of water by 34.6°C. Assume no heat losses occurred during this experiment. The density of $C_{14}H_{30}$ is 0.763 $g/cm^3$.
(i) Use relevant data from the Data Booklet to calculate the amount of heat released in this experiment.
(ii) Use the data above and your answer to (i) to calculate the energy produced by the combustion of 1 mol of $C_{14}H_{30}$.
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The elements of Group VII of the Periodic Table show variation in their properties.

(a) (i) Complete the table below, stating the colour of each element in its normal state at room temperature.

\[ \begin{array}{|c|c|c|} \hline \text{halogen} & \text{melting point/}^\circ \text{C} & \text{colour} \\ \hline \text{chlorine} & -101 & \\ \hline \text{bromine} & -7 & \\ \hline \text{iodine} & 114 & \\ \hline \end{array} \]

(ii) Briefly explain why the melting points of the halogens increase from chlorine to iodine.
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(b) The halogens form many interhalogen compounds in which two different halogens are combined. One such compound is bromine monochloride, BrCl.

(i) Complete the electronic configurations of chlorine and bromine.

\[ \begin{array}{|c|c|} \hline \text{chlorine} & 1s^22s^22p^6 \\ \hline \text{bromine} & 1s^22s^22p^6 \\ \hline \end{array} \]

(ii) Draw a 'dot-and-cross' diagram of the BrCl molecule. Show outermost electrons only.


(c) Interhalogen compounds like BrCl have similar properties to the halogens.

(i) By considering your answers to (a) and (b), predict the physical state of BrCl at room temperature. Explain your answer.

physical state .............................................

explanation ........................................................................................................................
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(ii) Suggest the colour of BrCl.
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(d) Cl_2 and BrCl each react with aqueous KI.

(i) Describe what would be seen when Cl_2 is bubbled through aqueous KI for several minutes.

initially .......................................................................................................................
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after several minutes ................................................................................................
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(ii) Construct an equation for the reaction that occurs.
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(iii) Suggest an equation for the reaction that occurs between BrCl and aqueous KI.
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(iv) How do Cl_2 and BrCl behave in these reactions?
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Compound Q is a viscous liquid which is very soluble in water. The $M_r$ of Q is 90.0.
Three possible structures for Q are shown below.

[Table_1]

a) (i) What type of isomerism do R, S and T show?
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(ii) What oxygen-containing functional groups are present in R, S and T? Give their full names.
R .......................................................... and ..........................................................
S .......................................................... and ..........................................................
T .......................................................... and ..........................................................

(iii) Which functional group(s) in (ii) will react with sodium carbonate?
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(iv) Which functional group(s) in (ii) will react with sodium metal?
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b) When 0.002 mol of Q is reacted with an excess of solid sodium carbonate, $\text{Na}_2\text{CO}_3$, 24 $\text{cm}^3$ of carbon dioxide, measured at room temperature and pressure, is produced.

(i) Calculate the amount, in moles, of carbon dioxide produced in this reaction.

(ii) Hence calculate the amount, in moles, of carbon dioxide produced by 1 mol of Q.

c) When 0.002 mol of Q is reacted with an excess of metallic sodium, 48 $\text{cm}^3$ of hydrogen, measured at room temperature and pressure, is produced.

(i) Calculate the amount, in moles, of hydrogen molecules produced in this reaction.

(ii) Hence calculate the amount, in moles, of hydrogen molecules produced by 1 mol of Q.

d) Use your answers to (b) and (c) to deduce which structure, R, S or T, corresponds to the structure of Q and write balanced equations for the reactions that occurred.

identity of Q is ........
equation for reaction with sodium carbonate
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equation for reaction with sodium metal
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The molecular formula $C_4H_9OH$ represents four different alcohols, $W$, $X$, $Y$ and $Z$.

(a) Draw the skeletal formula of $Z$. [1]

(b) Acidified potassium dichromate(VI) is used as an oxidising agent in organic chemistry.

Give the \textit{structural formula} of the organic product formed when each of the four alcohols above is heated under reflux with acidified potassium dichromate(VI). If you believe that no reaction occurs, write 'no reaction' in the box.   [4]

(c) One of the alcohols, $W$, $X$, $Y$ or $Z$, can be dehydrated to give more than one organic product.

Identify this alcohol and give the structural formulae of \textit{two} of the products.  [2]