AS LEVEL CHEMISTRY

PAPER 1
PRACTICE PAPER 15
(structured questions only)
Answer all questions
Max 80 marks

	
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Mark		……../80	……....%	Grade ………
		
Note – this paper only contains structured questions

1.       Define the term mass number of an atom.
The mass number of an isotope of nitrogen is 15. Deduce the number of each of the fundamental particles in an atom of 15N
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(Total 3 marks)
 
2.      (a)     A sample of ethanol vapour, C2H5OH (Mr = 46.0), was maintained at a pressure of 100 kPa and at a temperature of 366K.
(i)      State the ideal gas equation.
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(ii)     Use the ideal gas equation to calculate the volume, in cm3, that 1.36 g of ethanol vapour would occupy under these conditions.
(The gas constant R = 8.31 J K–1 mol–1)
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(b)     Magnesium nitride reacts with water to form magnesium hydroxide and ammonia.
(i)      Balance the equation, given below, for the reaction between magnesium nitride and water.
Mg3N2   +               H2O   →             Mg(OH)2   +              NH3
(ii)     Calculate the number of moles, and hence the number of molecules, of NH3 in 0.263 g of ammonia gas.
(The Avogadro constant L = 6.02 × 1023 mol–1)
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(c)     Sodium carbonate is manufactured in a two-stage process as shown by the equations below.
NaCl    +   NH3    +     CO2   +  H2O   →    NaHCO3   +   NH4Cl
2NaHCO3 →    Na2CO3  +   H2O   +   CO2
Calculate the maximum mass of sodium carbonate which could be obtained from 800 g of sodium chloride.
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(Total 13 marks)

3.          This question is about the elements in Period 3 from Na to P
(a)     (i)      Explain the meaning of the term first ionisation energy.
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(ii)     State and explain the general trend in first ionisation energies for the elements 
Na to P
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Explanation .........................................................................................
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(iii)     State which one of the elements from Na to P deviates from this general trend and explain why this occurs.
Trend ..................................................................................................
Explanation .........................................................................................
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(b)     State which one of the elements from Na to P has the highest melting point and explain your answer.
Element .......................................................................................................
Explanation ..................................................................................................
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(Total 11 marks)

 

4.          The chloride of an element Z reacts with water according to the following equation.
ZCl4(l) + 2H2O(l) → ZO2(s) + 4HCl(aq)
A 1.304 g sample of ZCl4 was added to water. The solid ZO2 was removed by filtration and the resulting solution was made up to 250 cm3 in a volumetric flask. A 25.0 cm3 portion of this solution was titrated against a 0.112 mol dm–3 solution of sodium hydroxide, of which 21.7 cm3 were required to reach the end point.
Use this information to calculate the number of moles of HCl produced and hence the number of moles of ZCl4 present in the sample. Calculate the relative molecular mass, Mr, of ZCl4.
From your answer deduce the relative atomic mass, Ar, of element Z and hence its identity.
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(Total 9 marks)
 
5.	
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(Total 9 marks)	

6.	Vanadium is an important metal. Ferrovanadium, an alloy of iron and vanadium, is used to make a strong type of vanadium-steel. Pure vanadium is used in nuclear reactors.
(a)     The table shows some standard enthalpy of formation data.
 
 	 	V2O5(s)	CaO(s)	
 	ΔHfθ / kJ mol−1	−1560	−635	

In the oldest method of extraction of vanadium, V2O5 is reacted with calcium at a high temperature.
5Ca(s)   +   V2O5(s)      2V(s)   +   5CaO(s)
Use data from the table and the equation to calculate the standard enthalpy change for this reaction.
State the type of reaction that V2O5 has undergone.
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(b)     Ferrovanadium is produced by the reaction of aluminium with a mixture of V2O5 and iron(III) oxide.
Write an equation for the reaction of aluminium with iron(III) oxide.
State the change in oxidation state of aluminium in this reaction.
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   (c)        Pure vanadium, for nuclear reactors, is formed by the reaction of hydrogen with purified VCl2
Write an equation for this reaction in which the only other product is HCl gas.
Deduce why this process produces pure vanadium, other than the fact that purified VCl2 is used.
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(Total 8 marks)

7.

(Total 9 marks)

 8.	Antimony is a solid element that is used in industry. The method used for the extraction of antimony depends on the grade of the ore.
(a)     Antimony can be extracted by reacting scrap iron with low-grade ores that contain antimony sulfide (Sb2S3).
(i)      Write an equation for the reaction of iron with antimony sulfide to form antimony and iron(II) sulfide.
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(1)
(ii)     Write a half-equation to show what happens to the iron atoms in this reaction.
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(1)

     (b)     In the first stage of the extraction of antimony from a high-grade ore, antimony sulfide is roasted in air to convert it into antimony(III) oxide (Sb2O3) and sulfur dioxide.
	Write an equation for this reaction.
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(1)
 (Total 3 marks)

9.     (a)     When using silver nitrate to test for the presence of chloride ions in an aqueous solution, it is important to add another reagent to prevent interference by any carbonate ions which would form a white precipitate of Ag2CO3
(i)      Identify this other reagent.
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(ii)     Write an equation to show how this other reagent reacts with sodium carbonate.
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(b)     The presence of some halide ions in solution can be detected using aqueous silver nitrate and aqueous ammonia.
(i)      Identify a halide ion which, on addition of aqueous silver nitrate, forms a precipitate that is insoluble in concentrated aqueous ammonia.
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(ii)     Identify a halide ion which cannot be detected using these reagents.
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(c)     A mixture of two precipitates, P and Q, was formed by adding aqueous silver nitrate to a solution containing two different halide ions. Precipitate P dissolved on addition of an excess of dilute aqueous ammonia. The remaining precipitate, Q, was filtered off.
(i)      Identify the halide ion in P.
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(ii)     Precipitate Q was soluble in concentrated aqueous ammonia. Identify the halide ion in Q.
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(2)
(Total 6 marks)

10.	In an experiment to determine its solubility in water, solid barium hydroxide was added to 100cm3 of water until there was an excess of the solid. The mixture was filtered and an excess of sulfuric acid was added to the filtrate. The barium sulfate produced was obtained from the reaction mixture, washed with cold water and dried. The mass of barium sulfate was then recorded.
(a)     Explain why the mixture was filtered before the addition of sulfuric acid.
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(b)     State how the barium sulfate produced was obtained from the reaction mixture.
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(c)     Explain why the barium sulfate was washed before it was dried.
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(d)     Write an equation for the reaction between barium hydroxide and sulfuric acid.
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(e)     In an experiment, 4.25 g of barium sulfate were formed when an excess of sulfuric acid was added to 100 cm3 of a saturated solution of barium hydroxide.
(i)      Use data from the Periodic Table to calculate the Mr of barium sulfate. 
Give your answer to one decimal place.
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(ii)     Calculate the amount, in moles, of BaSO4 in 4.25 g of barium sulfate.
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(iii)    Use your answer from part (ii) to calculate the mass of barium hydroxide(Mr = 171.3) present in 1 dm3 of saturated solution. Show your working.
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(f)     Barium sulfate is taken by mouth by patients so that an outline of a human digestive system can be viewed using X-rays. Explain why patients do not suffer any adverse effects from barium sulfate when it is known that solutions containing barium ions are toxic.
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(Total 9 marks)