AS & A Level Chemistry - 9701 Paper 2 2012 Summer Zone 1

Oxides are compounds which usually contain oxygen combined with one other element.
Oxides are classified as follows.
acidic alkaline amphoteric basic
(a) Using these terms only, complete the table to describe the oxides of the elements of the third period of the Periodic Table sodium to sulfur.
[Table: Na2O, MgO, Al2O3, SiO2, P4O10, SO2, Cl2O7 with the last column labeled as 'acidic' filled]
[4]

(b) Give the names of two elements from sodium to chlorine which form more than one oxide.
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[1]

(c) Sodium reacts with water.
(i) Describe, as fully as you can, what you would see when a piece of sodium is reacted with water.
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(ii) Write an equation for the reaction of sodium with water.
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[4]

(d) Sulfur dioxide is present in small, but significant, amounts in the Earth's atmosphere.
(i) State one way by which sulfur dioxide enters the atmosphere.
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(ii) Give the formula of another sulfur compound which is formed in the atmosphere from sulfur dioxide.
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(iii) What are the environmental consequences of the compound you have identified in (ii)?
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(e) Sulfur dioxide is used as a food preservative.
What property of sulfur dioxide enables it to act in this way?
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[1]

(f) Another sulfur compound which is present in the Earth's atmosphere is carbonyl sulfide, OCS. The sequence of atoms in the molecule is oxygen-carbon-sulfur and the molecule is not cyclic.
(i) Draw a 'dot-and-cross' diagram of the OCS molecule. Show outer electrons only.
(ii) Suggest a value for the O-C-S bond angle.
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[2]

Ammonium sulfate, (NH4)2SO4, is widely used as a fertiliser.
In order to determine its percentage purity, a sample of ammonium sulfate fertiliser was analysed by reacting a known amount with an excess of NaOH(aq) and then titrating the unreacted NaOH with dilute HCl.

(a) Ammonium sulfate reacts with NaOH in a 1:2 ratio. Complete and balance the equation for this reaction.
(NH4)2SO4 + 2NaOH → .......NH3 + ............... + ............... [2]

(b) A 5.00 g sample of a fertiliser containing (NH4)2SO4 was warmed with 50.0 cm3 (an excess) of 2.00 mol dm⁻³ NaOH.
When all of the ammonia had been driven off, the solution was cooled.
The remaining NaOH was then titrated with 1.00 mol dm⁻³ HCl and 31.2 cm3 were required for neutralisation.

(i) Write a balanced equation for the reaction between NaOH and HCl.
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(ii) Calculate the amount, in moles, of HCl in 31.2 cm3 of 1.00 mol dm⁻³ HCl.
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(iii) Calculate the amount, in moles, of NaOH in 50.0 cm3 of 2.00 mol dm⁻³ NaOH.
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(iv) Use your answers to (i), (ii) and (iii) to calculate the amount, in moles, of NaOH used up in the reaction with (NH4)2SO4.
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(v) Use your answer to (iv) and the equation in (a) to calculate the amount, in moles, of (NH4)2SO4 that reacted with NaOH.
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(vi) Use your answer to (v) to calculate the mass of (NH4)2SO4 that reacted with NaOH.
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(vii) Hence, calculate the percentage purity of the ammonium sulfate fertiliser. [7]

(a) Define, with the aid of an equation which includes state symbols, the standard enthalpy change of formation of carbon dioxide.
equation ................................................................................................................................................
definition ................................................................................................................................................
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(b) Relevant $\Delta H_f^{\circ}$ values for the reaction that synthesises methanol are given in the table.

[Table_1]

(i) Use these values to calculate $\Delta H_{reaction}^{\circ}$ for this synthesis of methanol.
Include a sign in your answer.

$$\text{CO}_2(g) + 3\text{H}_2(g) \leftrightarrow \text{CH}_3\text{OH}(g) + \text{H}_2\text{O}(g)$$

$\Delta H_{reaction}^{\circ}$ = .......................... kJ mol^{-1}

(ii) Suggest one possible environmental advantage of this reaction. Explain your answer.
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(c) The synthesis of methanol is carried out at about 500 K with a pressure of between 40 and 100 atmospheres (between $4 \times 10^6$ Pa and $10 \times 10^7$ Pa) and using a catalyst. The use of such conditions will affect both the rate of reaction and the equilibrium yield.

In the spaces below, explain the effects of higher temperature, higher pressure, and the use of a catalyst on the equilibrium yield of methanol.

higher temperature
effect .....................................................................................................................................
explanation ............................................................................................................................
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higher pressure
effect .....................................................................................................................................
explanation ............................................................................................................................
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use of catalyst
effect .....................................................................................................................................
explanation ............................................................................................................................
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One method of preparing ethene in a school or college laboratory is from ethanol by using the apparatus shown below.

(a) (i) Write a balanced equation for this reaction.
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(ii) What extit{type of reaction} is this?
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(iii) Give the chemical name of a reagent other than pumice that could be used to carry out this reaction. It is not necessary to use the same apparatus.
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(b) Ethene is bubbled into two separate test-tubes, one containing aqueous hydrogen bromide and the other containing cold, dilute acidified potassium manganate(VII).
In extit{each case}, describe any colour changes you would see and give the structural formula of the organic product.
[Table_1]
aqueous hydrogen bromide
colour at start
colour after reaction
structural formula of organic product
cold, dilute acidified potassium manganate(VII)
colour at start
colour after reaction
structural formula of organic product

(c) Cyclohexene has the following structural formula.

(i) What is the molecular formula of cyclohexene?
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(ii) Draw the structural formula of the compound formed when cyclohexene is reacted with bromine.
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(iii) State as fully as you can what extit{type of reaction} this is.
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(iv) Draw the structural formula of the compound formed when cyclohexene is reacted with hot concentrated acidified potassium manganate(VII).

Organic compounds which contain oxygen may contain alcohol, aldehyde, carboxylic acid, ester or ketone functional groups. The functional groups may be identified by their reactions with specific reagents.

Compound $X$ has the empirical formula $CH_2O$ and $M_r$ of 90.

(a) There is no reaction when $X$ is treated with $NaHCO_3$.
What functional group does this test show to be not present in $X$?
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[1]

(b) When 0.600 g of $X$ is reacted with an excess of $Na$, 160 $cm^3$ of $H_2$, measured at room temperature and pressure, is produced.

(i) What functional group does this reaction show to be present in $X$?
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(ii) Use the data to calculate the amount, in moles, of hydrogen atoms produced from 0.600 g of $X$.

(iii) Hence, show that each molecule of $X$ contains two of the functional groups you have given in (i).
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(c) When $X$ is warmed with Fehling’s reagent, a brick red precipitate is formed. Treatment of $X$ with 2,4-dinitrophenylhydrazine reagent produces an orange solid.

(i) What functional group do these reactions show to be present in $X$?
Draw the displayed formula of this functional group.

(ii) Use your answers to (b)(i), (b)(ii) and (c)(i) to deduce the structural formula of $X$.

(iii) What is the structural formula of the organic product of the reaction of $X$ with Fehling’s reagent?
[3]

(d) Compound $X$ can be both oxidised and reduced.

(i) Give the structural formula of the compound formed when $X$ is reacted with $NaBH_4$ under suitable conditions.

(ii) Give the structural formula of the compound formed when $X$ is heated under reflux with acidified $K_2Cr_2O_7$.
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