Chemistry · Paper 2B · 2021

6 questions 🇹🇿 NECTA ✓ Official NECTA answers

DSEE 🇹🇿 NECTA ✓ Official NECTA answers

Chemistry · Paper 2B · 2021

6 questions

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Questions (6)

Section B

1. 0 marks

(vi) Repeat procedure (i) to (v) at different temperatures as shown in the following table. Experimental Data | Experiment | Time (s) | Temperature °C) | |---|---|---| | 1 | | 40 | | 2 | | 50 | | 3 | | 60 | | 4 | | 70 | | 5 | | 80 | (a) Record the room temperature in Kelvin (K). (b) Why did the mark M disappear? (c) Complete the table by filling the blank columns. (d) (i) Write a balanced chemical equation for the reaction taking place between EE and FF. Show all the state symbols. (ii) Write the ionic equation for the reaction between EE and FF. (e) Plot a graph of time(s) against temperature (K). (f) What conclusion can be drawn from the graph that you plotted in (e)?

(a) Record the room temperature in Kelvin (K). 0 mk

(a(i)) What was the colour change observed during this titration experiment? 0 mk

(a(ii)) What was the volume of the pipette used? 0 mk

(b) Why did the mark M disappear? 0 mk

((a)(i) Calculate the average volume of solution E2 that was used to neutralize solution E1. 1 mk

(a(iii) Calculate the average volume of solution E2 that was used to neutralize solution E1. 0 mk

(d (i)) Write a balanced chemical equation for the reaction taking place between EE and FF. Show all the state symbols. 0 mk

(b) Write a balanced chemical equation (include state symbols) between E2 and E1 and the corresponding ionic equation. 1 mk

(d (ii) Write the ionic equation for the reaction between EE and FF. 0 mk

(e) Plot a graph of time(s) against temperature (K). 0 mk

(f) What conclusion can be drawn from the graph that you plotted in (e)? 0 mk

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2. 0 marks

Sample O is a simple salt containing one cation and one anion. Carefully, carry out qualitative analysis experiment to identify the ions present in the salt based on the following tests: (a) Appearance of the sample. (b) Action of heat on the sample. (c) Action of concentrated sulphuric acid on the sample then warm. (d) The sample dissolved in the water. (e) Action of aqueous sodium hydroxide on the solution of the sample. (f) Action of potassium hexacyanoferrate(II) solution on the solution of the sample followed by dilute HCl. (g) Action of ferrous sulphate solution on the solution of the sample followed by concentrated H₂SO₄ along the side of test tube. Questions (i) Prepare a relevant Table showing the qualitative analysis results. (ii) Write a balanced chemical equation for the test at experimental test (b). (iii) Write a balanced chemical equation between the sample and sodium carbonate.

(a) Record the room temperature in Kelvin (K). 0 mk

(i) Prepare a relevant Table showing the qualitative analysis results. 0 mk

(b) Why did the mark M disappear? 0 mk

(ii) Write a balanced chemical equation for the test at experimental test (b). 0 mk

(iii) Write a balanced chemical equation between the sample and sodium carbonate. 0 mk

(d(i)) Write a balanced chemical equation for the reaction taking place between EE and FF. Show all the state symbols. 0 mk

(d(ii)) Write the ionic equation for the reaction between EE and FF. 0 mk

(e) Plot a graph of time(s) against temperature (K). 0 mk

(f) What conclusion can be drawn from the graph that you plotted in (e)? 0 mk

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