AS LEVEL CHEMISTRY

ASSESSMENT POINT 1
(TOPICS 1 AND 2)
Answer all questions
Max 80 marks

	
Name		……………………………………………………………..

Mark		……../80	……....%	Grade ………

1.     (a)     Complete the following table.
 
 	Relative mass	Relative charge	
Proton	 	 	
Electron	 	 	

(2)
(b)     An atom of element Q contains the same number of neutrons as are found in an atom of 27A1. An atom of Q also contains 14 protons.
(i)      Give the number of protons in an atom of 27A1.
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(ii)     Deduce the symbol, including mass number and atomic number, for this atom of element Q.
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(3)
(c)     Define the term relative atomic mass of an element.
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(2)
(d)     The table below gives the relative abundance of each isotope in a mass spectrum of a sample of magnesium.
 
m/z	24	25	26	
Relative abundance (%)	73.5	10.1	16.4	

Use the data above to calculate the relative atomic mass of this sample of magnesium.
Give your answer to one decimal place.
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(2)
(e)     State how the relative molecular mass of a covalent compound is obtained from its mass spectrum.
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(1)
(Total 10 marks)
2.	Tellurium is the element with atomic number of 52
(a)     Using information from the Periodic Table, complete the electron configuration of tellurium.
[Kr] .................................................................................................................
(1)
(b)     The mass spectrum of a sample of tellurium is shown in the graph.

(i)      Use the graph to calculate the relative atomic mass of this sample of tellurium.
Give your answer to one decimal place.
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(3)
(ii)     Suggest what might cause the relative atomic mass of this sample to be different from the relative atomic mass given in the Periodic Table.
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(1)
(c)     Write an equation for the reaction that occurs when a tellurium ion hits the detector.
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(1)

(d)     State the m / z value of the ions that produce the biggest current at the detector when the spectrum in the graph is recorded.
Give a reason for your answer.
m / z value ......................................................................................................
Reason ..........................................................................................................
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(2)
(e)     The mass spectrum of tellurium also has a small peak at m / z = 64
Explain the existence of this peak.
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(2)
(f)     Predict whether the atomic radius of 124Te is larger than, smaller than or the same as the atomic radius of 130Te
Explain your answer.
Atomic radius of 124Te compared to 130Te ......................................................
Explanation ....................................................................................................
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(2)
(Total 12 marks)

3.	The values of the first ionisation energies of neon, sodium and magnesium are 2080, 494 and 736 kJ mol–1, respectively.
(a)     Explain the meaning of the term first ionisation of an atom.
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(2)
(b)     Write an equation to illustrate the process occurring when the second ionisation energy of magnesium is measured.
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(2)
(c)     Explain why the value of the first ionisation energy of magnesium is higher than that of sodium.
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(2)
(d)     Explain why the value of the first ionisation energy of neon is higher than that of sodium.
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(2)
(Total 8 marks)

4.          A metal carbonate MCO3 reacts with hydrochloric acid as shown in the following equation.
MCO3  +  2HCl  →  MCl2  +  H2O  +  CO2
A 0.548 g sample of MCO3 reacted completely with 30.7 cm3 of 0.424 mol dm–3 hydrochloric acid.
(a)    (i)      Calculate the amount, in moles, of HCl which reacted with 0.548 g MCO3
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(1)
(ii)     Calculate the amount, in moles, of MCO3 in 0.548 g.
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(1)
(iii)     Calculate the relative formula mass of MCO3
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(1)
(b)     Use your answer from part (a)(iii) to deduce the relative atomic mass of metal M and suggest its identity.
(If you have been unable to calculate a value for the relative formula mass of MCO3 you should assume it to be 147.6 but this is not the correct answer.)
Relative atomic mass ..................................................................................
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Identity of M ..................................................................................................
(2)
(Total 5 marks)

 

5.	A sample of hydrated nickel sulfate (NiSO4.xH2O) with a mass of 2.287 g was heated to remove all water of crystallisation. The solid remaining had a mass of 1.344 g.
(a)     Calculate the value of the integer x.
Show your working.
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(4)
(b)     Suggest how a student doing this experiment could check that all the water had been removed.
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(2)
(Total 6 marks)

6.	A teacher noticed that a student had not cleared a large air bubble from below the burette tap in preparing the burette for use before starting the titration. This air bubble was ejected during the first titration of the volumetric flask mixture.
(a)     State the effect that this mistake would have on the value of the first titre.
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(1)
(b)    State and explain the effect, if any, that this mistake would have on the average titre for this experiment.
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(2)
(Total 3 marks)

7.		
	(a)

(b)

(c)

(d)	

	(e)

(f)

(g)

(h)

	

	(i)

(j)	
(Total 14 marks)	
8.	Some airbags in cars contain sodium azide (NaN3).
(a)     Sodium azide is made by reacting dinitrogen monoxide gas with sodium amide (NaNH2) as shown by the equation.
2NaNH2  +  N2O    NaN3   +   NaOH   +   NH3
Calculate the mass of sodium amide needed to obtain 550 g of sodium azide, assuming there is a 95.0% yield of sodium azide.
Give your answer to 3 significant figures.
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(5)

(b)     If a car is involved in a serious collision, the sodium azide decomposes to form sodium and nitrogen as shown in the equation.
2NaN3(s)      2Na(s)   +   3N2(g)
The nitrogen produced then inflates the airbag to a volume of 7.50 × 10−2 m3 at a pressure of 150 kPa and temperature of 35 °C.
Calculate the minimum mass of sodium azide that must decompose.
(The gas constant R = 8.31 J K−1 mol−1)
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(6)

(c)      Sodium azide is toxic. It can be destroyed by reaction with an acidified solution of nitrous acid 	(HNO2) as shown in the equation.
2NaN3  +  2HNO2  +  2HCl    3N2  +  2NO  +  2NaCl  +  2H2O
(i)      A 500 cm3 volume of the nitrous acid solution was used to destroy completely 150 g of the sodium azide.
Calculate the concentration, in mol dm−3, of the nitrous acid used.
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 (3)
(ii)     Nitrous acid decomposes on heating.
Balance the following equation for this reaction.
........HNO2     .......HNO3   +   .......NO   +   .......H2O
(1)
(Total 15 marks)
9.	Zinc is similar to Group 2 metals and forms compounds containing Zn2+ ions.
Write an equation for the thermal decomposition of zinc carbonate to zinc oxide.
Calculate the percentage atom economy for the formation of zinc oxide from zinc carbonate in this reaction.
Equation ..................................................................................................................
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Percentage atom economy .....................................................................................
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(Total 3 marks)

10.	Which one of the following does not have a pair of s electrons in its highest filled electron energy sub-level?
A       H−
B       Mg
C       P3+
D       Ar
(Total 1 mark)

11.	Assuming that chlorine exists as two isotopes, and that hydrogen and carbon exist as one isotope each, how many molecular ion peaks will be shown in the mass spectrum of C4H6Cl4?
A       2
B       3
C       4
D       5
(Total 1 mark)

12.	The removal of silicon dioxide with limestone in the Blast Furnace can be represented by the following equation.
CaCO3(s) + SiO2(s) → CaSiO3(l) + CO2(g)
The minimum mass of calcium carbonate needed to remove 1.00 tonne (1000 kg) of silicon dioxide is
A       0.46 tonne
B       0.60 tonne
C       1.67 tonne
D       2.18 tonne
(Total 1 mark)

13.	If 1.00 g of propanone (C3H6O) was vapourised at 100 °C and 100 kPa pressure, the volume in m3 of gas formed would be
A       31.0
B       8.31
C       0.534
D       5.34 × 10−4
(Total 1 mark)