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AQA Jun 2017 Paper 2 Q2
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![0 2The rate equation for the reaction between compounds A and B is rate = k [A]2[B] Figure 2 shows how, in an experiment, the concentration of A changes with time, t, in this reaction. Figure 2 0 2 . 1 0 2 . 2 *04* Draw a tangent to the curve at t = 0 Use this tangent to deduce the initial rate of the reaction. Initial rate [1 mark] [1 mark] mol dm3s1 IB/M/Jun17/7405/2<br />
0 2 . 3 The experiment was repeated at the same temperature and with the same initial concentration of B but with a different initial concentration of A. The new initial rate was 1.7 times greater than in the original experiment. Calculate the new initial concentration of A. [2 marks]Initial concentration of A mol dm3 Turn over for the next question *05* Turn overIB/M/Jun17/7405/2<br />](https://learnah.org/wp-content/uploads/2018/08/June_2017_QP_-_Paper_2_AQA_Chemistry_A-Level_2-0.jpg)
![MARK SCHEMEA-LEVEL CHEMISTRY7405/2JUNE 2017 Answers Mark Additional Comments/Guidance Straight line through (0.00, 0.50) which cuts time axis at between 5 and 12.5 secs OR conc 0.3 at time between 2s and 5s Mark is for correct calculation of their gradient : e.g. 0.50/11 = 0.045 or 4.510-2 (mol dm-3 s-1) [A] increases by 1.7 new[A]2 = 1.7(0.50)2 = 0.425 new[A] = 1.300.50 = 0.65 (mol dm-3) 2 sfs min New [A] = 0.65 (mol dm-3) 2 sfs min If tangent does not touch 0.5 mol dm-3 then CE=0 for 2.1 and 2.2. no tangent scores 0 in 2.1 and 2.2. If tangent does not touch 0.5 mol dm-3 then CE=0 for 2.1 and 2.2 Ignore negative sign (Expect a value between 0.04 and 0.1 Award 2 for 0.65 Award 1 mark for an AE using a correct method If candidate use their rate then CE=0 0.85 scores 1 ifshown 16 of 32 Question 02.1 02.2 02.3 Total<br />](https://learnah.org/wp-content/uploads/2018/08/June_2017_MS_-_Paper_2_AQA_Chemistry_A-Level_2.jpg)