Test Exam:Chemistry - 5th Year Christmas Test
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Time: 2 hours
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Q2.
(a) Describe John Daltons image of the atom. (5)
(b) JJ Thomson calculated the e/m of the electrons. What does the e/m stand for? (5)
(c) Explain the difference between an emission line spectrum and an absorption spectrum. (5)
(d) What colour is observed when a sample of Barium is burnt? (5)
(e) Write the equation linking energy and frequency of a wave. (5)
(f) The idea of electrons having a wave motion was suggested by a French Scientist. Name him. (5)
(g) Describe using a diagram the shapes of both s and p orbitals. (5)
(h) Explain the term energy level. (5)
(i) How many sublevels are present in the n=3 main energy level. (5)
(j) What is an orbital?. (5)
Q.3
(a) Define (i) Catalyst and (ii) Activation energy. (12)
(b) 25cm3 of a standard 0.2M Na2S2O3 solution was diluted to 100cm3 and poured into a conical flask; 10cm3 of dilute HCL was added. The time was measured for the solution to turn cloudy. The experiment was repeated at different temperatures and the folloqing results obtained:
Temp/C 20 30 40 50 60 70 80 Time/Sec 39 27 22 18 12 10 8
(i) Why was the standard 0.2M solution diluted? (6)
(ii) What steps would you have taken to ensure that the same degree of cloudiness was taken for each temperature? (6)
(iii) Plot the graph of rate (1/t) agains temperature. (18)
(iv) If the reaction had been carried out at 45C what time would have elapsed before the solution became cloudy. (6)
(v) Draw an energy profile diagram of a reaction. On the diagram show the effect of introducing a catalyst. (9)
(vi) Explain autocatalysis and give an example. (5)
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