Benzenediazonium chloride, C6H5N2Cl, decomposes in water as shown in the following equation. C6H5N2Cl(aq) + H2O(l) → C6H5OH(aq) + N2(g) + HCl(aq) A solution of 0.0750moldm¬³ of C6H5N2Cl(aq) decomposes at a constant temperature of 50°C. The volume of nitrogen gas, N2(g), collected is recorded every 5 minutes for 45 minutes.

1. (a)Draw a labelled diagram to show how the apparatus could be set up to carry out this experiment.[3]
2. (b)(i)On Fig. 2.1, draw a tangent to the curve at t = 0 mins. Calculate the initial rate of reaction in cm³ min-1. initial rate of reaction = .............................................................. cm³ min-1[2]
3. (b)(ii)Explain why the initial rate of reaction is calculated at t = 0 mins rather than dividing the total volume of gas produced by the time taken to produce it.[1]
4. (b)(iii)Describe how the curve in Fig. 2.1 would be different, if at all, if the atmospheric pressure increases. All other conditions stay the same.[1]
5. (b)(iv)On Fig. 2.1, draw a second curve to show the graph produced if the same volume of 0.0375 moldm-3 C6H5N2Cl(aq) decomposes at a constant temperature of 50°C. All other conditions stay the same.[1]
6. (c)(i)Complete the table to calculate the values for the rate of N₂ production. Give your answers to three significant figures. Table 2.1 concentration of C6H5N2Cl(aq) / moldm-3 time taken to collect 0.0150 dm³ of N₂/s rate of N2 production /dm³s-1 0.500 21 0.400 33 0.300 48 0.200 64 0.100 122 [1]
7. (c)(ii)The reaction is first order and obeys the following rate equation. rate = k [C6H5N2Cl] Explain how the data in Table 2.1 supports this statement.[1]
8. (c)(iii)State the dependent variable in this investigation.[1]
9. (c)(iv)The student wants to perform a similar experiment using 0.200 moldm¯³ C6H5N2Cl(aq). Describe how the student should make a standard solution of 100.0 cm³ of 0.200 mol dm-3 C6H5N2Cl(aq) starting from a solution of 0.500 moldm−3 C6H5N2Cl(aq). Give the name and size of any key apparatus which should be used and describe how the student should ensure the volume is exactly 100.0cm³. Write your answer using a series of numbered steps.[3]
10. (c)(v)Explain why (iv) must be carried out at a temperature below 5°C.[1]
11. (d)(i)The student's final yield was 52%. They had not spilled any reagents or products. Suggest two reasons why the student's yield was lower than 100%. Assume no errors were made in the measurement of any substances. reason 1: reason 2:[2]
12. (d)(ii)Explain why the solid dye should be dried before assessing the melting point.[1]

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