A-level chemistry aqa practice paper 1 topics

Which statement is correct about this reaction?
1.
[Co(NH3)6]2+ + 3H2NCH2CH2NH2 → [Co(H2NCH2CH2NH2)3]2+ + 6NH3


A The co-ordination number of cobalt decreases.

B The enthalpy change is large and positive.

C The entropy change is large and positive.

D The shape of the complex changes from octahedral.

(Total 1 mark)

This question is about emissions of oxides of nitrogen from petrol and diesel engines.
2.
(a) Explain how oxides of nitrogen are formed in engines.

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(2)

(b) State why it is desirable to decrease emissions of oxides of nitrogen from vehicles.

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(1)




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,(c) Modern diesel vehicles use diesel exhaust fluids, such as AdBlue, to decrease emissions of
oxides of nitrogen.

AdBlue reacts with water in the hot exhaust gases to form ammonia.
In the presence of a catalyst the ammonia reacts with oxides of nitrogen to form nitrogen
and water.

Give the oxidation state of nitrogen in each of NO2, NH3 and N2

Complete the equation for the reaction between NO2 and NH3

Oxidation state of nitrogen in


NO2________ NH3________ N2________

Equation


________ NO2 + ________ NH3 → ________ N2 + ________ H2O
(2)

(d) Petrol vehicles have a catalytic converter which decreases emissions of oxides of nitrogen.
Platinum in the catalytic converter acts as a heterogeneous catalyst.

State the meaning of the term heterogeneous catalyst.

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(2)

(e) Some carbon particulates are also formed in both diesel and petrol vehicles.

Explain why carbon particulates are formed.

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(1)
(Total 8 marks)




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, This question is about oxides.
3.
(a) Sodium oxide forms a solution with a higher pH than magnesium oxide when equal
amounts, in moles, of each oxide are added separately to equal volumes of water.

State why both oxides form alkaline solutions.

Suggest why sodium oxide forms a solution with a higher pH than the solution formed from
magnesium oxide.

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(2)

(b) Give an equation for the reaction between phosphorus(V) oxide and water.

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(1)

(c) In the Contact process, sulfur(IV) oxide is converted into sulfur(VI) oxide using vanadium(V)
oxide as a catalyst.

Give two equations to show how the vanadium(V) oxide acts as a catalyst in this process.




Equation 1 __________________________________________________________




Equation 2 __________________________________________________________
(2)
(Total 5 marks)




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, (a) Explain why complexes formed from transition metal ions are coloured.
4.
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(3)

The iron content of iron tablets can be determined by colorimetry.

Method:
• Dissolve a tablet in sulfuric acid.
• Oxidise all the iron from the tablet to Fe 3+(aq).
• Convert the Fe 3+(aq) into a complex that absorbs light of wavelength 490 nm
• Make the solution up to 250 cm 3
• Measure the absorbance of light at 490 nm with a colorimeter.
• Use a calibration graph to find the concentration of the iron(III) complex.

(b) Calculate the energy, in J, gained by each excited electron in the absorption at 490 nm

Speed of light, c = 3.00 x 108 m s–1
Planck constant, h = 6.63 x 10–34 J s




Energy gained by each electron _______________ J
(3)




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