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Chemistry · Paper 2A · 2022

6 questions

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Questions (6)

Section A

1. 0 marks

Experimental procedure: (i) Put water in a 250 or 300 cm³ beaker about two thirds and heat the content to about 100˚C. Use this as water bath. (ii) Measure 10 cm³ portions of P1 and P2 and transfer them into two separate test tubes (iii) Put the test tubes in the water bath. (iv) Allow the contents of the two test tubes to warm up to 50˚C. (v) Pour both solutions, P1 and P2, into a 50 cm³ beaker and immediately start a stopwatch and record the time taken for the purple color to disappear. (vi) Repeat procedure (ii) to (v) except that instead of 50 ºC in procedure (iv) use temperatures, 60 ˚C, 70 ˚C and 80 ˚C. a) Complete the following Table Table of Results Temperature, T 1/T (K⁻¹) Time, t (s) Rate (1/t) (s⁻¹) log(1/t) °C K 50 60 70 80 b) Write a balanced ionic equation for the reaction. c) With reference to the results in (a), explain the relationship between temperature and reaction time. d) Plot a graph of log (1/t) as a function of 1/T. e) Determine the activation energy of the reaction given that the Arrhenius equation can be presented by the relation log(1/t) = logA - Ea / 2.303R * (1/T), where E is the activation energy and R is the gas constant = 8.314 Jmol⁻¹K⁻¹

(a) Complete the following Table Table of Results Temperature, T 1/T (K⁻¹) Time, t (s) Rate (1/t) (s⁻¹) log(1/t) °C K 50 60 70 80 0 mk
(a)(i)) What is the volume of the pipette used? 0 mk
(a)(ii) Present your results in an appropriate tabular form. 0 mk
(b) Write a balanced ionic equation for the reaction. 0 mk
(c) With reference to the results in (a), explain the relationship between temperature and reaction time. 0 mk
(b)) What is the colour of the indicator before and at the equivalence point? 0 mk
(c)) Calculate the concentration of HCl in solution B in mol dm -3 . 0 mk
(d) Plot a graph of log (1/t) as a function of 1/T. 0 mk
(d)) Calculate the concentration (in mol dm -3 ) of Na 2 CO 3 after dilution of solution A. 0 mk
(e) Determine the activation energy of the reaction given that the Arrhenius equation can be presented by the relation log(1/t) = logA - Ea / 2.303R * (1/T), where E is the activation energy and R is the gas constant = 8.314 Jmol⁻¹K⁻¹ 0 mk
(e)) Calculate the concentration (in mol dm -3 ) of Na 2 CO 3 before dilution of solution A. 0 mk
(f)) If the diluted 10 ml of solution A contains 0.888 g of impure sodium carbonate, what is the percentage composition of sodium carbonate in the solution? 0 mk
(g)) If solution A was made by dissolving a known mass of impure sodium carbonate and distilled water was added to make the solution up to 250cm 3 in a graduated flask, give one reason why the impure sodium carbonate was dissolved in water first and then made up to 250 cm 3 of solution, rather than being dissolved in 250 cm 3 of distilled water. 0 mk

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2. 0 marks

Sample from the industry was brought to the college laboratory as X. Perform systematic qualitative analyses to identify the cation and anion which cause the contamination of water. Prepare a relevant Table showing the qualitative analysis results. Base your experiment on the listed tests and then answer the questions that follow: (i) Appearance of sample X. (ii) Action of heat on sample X in a test tube (iii) Action of dilute sulphuric acid on a solid sample. (iv) Action of concentrated sulphuric acid on solid sample. (v) Flame test. (vi) Solubility of the sample. (vii) Action of dilute hydrochloric acid to a sample solution. (viii) Action of aqueous ammonia to the original sample solution followed by ammonium oxalate. (a) What are the cation and anion present in the water source? (b) Write the reaction equation to indicate what took place in test (iii).

(a)) Complete the following Table Table of Results Temperature, T 1   1  1 K1 Time, t (s) Rate  S1  log  T t  t °C K 50 60 70 80 0 mk
(a) What are the cation and anion present in the water source? 0 mk
(b) Write the reaction equation to indicate what took place in test (iii). 0 mk
(b)) Write a balanced ionic equation for the reaction. 0 mk
(c)) With reference to the results in (a), explain the relationship between temperature and reaction time 0 mk
(d)) Plot a graph of log (1/t) as a function of 1/T. 0 mk

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