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CIE Jun 2014 v2 Paper 5 Q2
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![PMT Nitrogen(II) oxide, NO, can be oxidised by ozone, O3, in the atmosphere to form nitrogen(IV) oxide, NO2. It is possible to simulate this process in the laboratory to measure the rate at which this reaction takes place. In this experiment, nitrogen(II) oxide is reacted with ozone. Since the concentration of nitrogen(II) oxide, [NO], in the air is very low, specialist equipment is required and [NO] oxide is measured as the number of molecules present in a volume of 1 cm3. The results obtained from the experiment are shown below. time / s concentration of NO / 108 molecules cm3 0 30 60 90 120 150 180 210 240 270 300 27.0 21.9 17.7 14.4 13.2 9.45 7.66 6.21 5.03 4.08 3.31UCLES 2014 9701/52/M/J/14<br />
(a) Use the results obtained to plot a graph to show the relationship between [NO] and time. 27.0 PMT 25.0 23.0 21.0 19.0 17.0 15.0 3m c s e u c e o m 8 0 1 / ] O N 13.0 11.0 9.0 7.0 5.0 3.0 50 100 150 200 250 300 350 400UCLES 2014 9701/52/M/J/14 [Turn over<br />
PMT (b) On your graph circle the single result that you consider to be the most anomalous. Suggest a reason why anomalous results may occur during an experiment to measure the rate of a reaction.[2] (c) Use construction lines at concentrations of nitrogen(II) oxide equal to 13.5108 molecules cm3 and 6.75108 molecules cm3 to determine the order of reaction with respect to nitrogen(II) oxide. Show the construction lines on your graph and your working. (d) (i) Use your graph to calculate the initial rate of the reaction. [3] [2] (ii) In the reaction between ozone and nitrogen(II) oxide the order of reaction with respect to ozone is 1. In the experiment the initial concentration of ozone used was 41011 molecules cm3. Calculate the value of the rate constant for the reaction and give its units.UCLES 2014 9701/52/M/J/14 [2]<br />
(e) 1 mole contains 6.021023 particles. Convert the initial rate in (d)(i) to a value with units of mol dm3 s1. (If you have no answer to (d)(i) you may use 3.0105 as the value of the initial rate.) PMT [2] (f) The concentration of ozone used in the experiment is considerably greater than the concentration of nitrogen(II) oxide. Explain why this is necessary for the experiment, in order to determine the order with respect to nitrogen(II) oxide.[2] [Total: 15]UCLES 2014 9701/52/M/J/14 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/June_2014_v2_QP_-_Paper_5_CIE_Chemistry_A-level_2-0.jpg)
![Page 3 (a) (b) (c) Mark Scheme GCE AS/A LEVELMay/June 2014 Syllabus 9701 Paper 52 2 marks awarded unless: (i) The curve is clearly not smooth or has a point of inflexion or is in the wrong position (ii) A point is clearly not in the correct position [2] [2] Point at 120 s is the most anomalous Difficult to measure very small concentrations / volume OR concentration / volume measured before the recorded time OR time recorded later than the measured concentration EITHER Draws appropriate construction lines Read two half-lives from graph as between 95 and 105 s Because half-lives are equal, identifies the reaction as first order OR Draws tangents to the curve at the points Correctly calculates gradients of the two lines OR the ratio of gradients Because shallower gradient is half of the steeper gradient, the reaction is first order [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [2] [3] [2] [1] [2] [2] [1] [1] [1] [1] [2] (d) (i) Draws suitable tangent at t = 0 Calculates gradient correctly for any line drawn at t = 0. (e) (f) (ii) Calculates correctly a value for: 11 8 k = ans(d(i)) / (2710 )(410 3 gives units as cm molecules 1 1 Gives initial rate (gradient) as ans(d(i))/(6.02 10 Completes calculation correctly 23 The ozone concentration should remain (nearly) constant during the experiment So that the rate depends only on the concentration of NOCambridge International Examinations 2014<br />](https://learnah.org/wp-content/uploads/2018/08/June_2014_v2_MS_-_Paper_5_CIE_Chemistry_A-level_2.jpg)