Edexcel IAL Chemistry AS Plotting Two Variables

Edexcel IAL Chemistry AS Plotting Two Variables
Pearson Edexcel International Advanced Subsidiary/Advanced Level in Chemistry, Issue 1, September 2017Chemistry XCH11/YCH11

Practise Edexcel IAL Chemistry plotting two variables with sensible scales, labelled axes, accurate points and best-fit lines or curves for practical data.

How this is tested

  • Choose graph scales so plotted points cover enough grid space, with variables and units on the correct axes.
  • Plot experimental data within half a small square and include all required table points or transformed values.
  • Draw the specified best-fit line or curve, including origin or anomaly decisions when the mark scheme states them.

Question 3(b)(i)

[Maximum number: 3]

A group of students carried out an experiment to investigate the reaction between potassium manganate(VII) and ethanedioate ions in acid conditions.

The equation for the reaction is shown.

2MnO4−(aq)+16H+(aq)+5C2O42−(aq)→2Mn2+(aq)+10CO2( g)+8H2O(l)2 \mathrm{MnO}_{4}^{-}(\mathrm{aq})+16 \mathrm{H}^{+}(\mathrm{aq})+5 \mathrm{C}_{2} \mathrm{O}_{4}^{2-}(\mathrm{aq}) \rightarrow 2 \mathrm{Mn}^{2+}(\mathrm{aq})+10 \mathrm{CO}_{2}(\mathrm{~g})+8 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

Procedure

Step 1 Measure 10.0 cm310.0 \mathrm{~cm}^{3} of potassium iodide solution into each of eight conical flasks.

Step 2 Measure 100.0 cm3100.0 \mathrm{~cm}^{3} of ethanedioic acid solution into a 250 cm3250 \mathrm{~cm}^{3} beaker.
Add 25.0 cm325.0 \mathrm{~cm}^{3} of potassium manganate(VII) solution and 5.0 cm35.0 \mathrm{~cm}^{3} sulfuric acid to the beaker. Mix the contents of the beaker and start a timer.

Step 3 Immediately withdraw 10.0 cm310.0 \mathrm{~cm}^{3} of reaction mixture and add it to the first conical flask containing (excess) potassium iodide solution.

Step 4 Continue removing 10.0 cm310.0 \mathrm{~cm}^{3} of reaction mixture every minute for seven minutes. Each time, add the reaction mixture to a new conical flask containing the potassium iodide solution.

Step 5 Using starch as an indicator, titrate the iodine formed in the conical flasks with sodium thiosulfate solution.

The equation for the reaction in Step 3 is shown.

2MnO4−(aq)+16H+(aq)+10I−(aq)→2Mn2+(aq)+5I2(aq)+8H2O(l)2 \mathrm{MnO}_{4}^{-}(\mathrm{aq})+16 \mathrm{H}^{+}(\mathrm{aq})+10 \mathrm{I}^{-}(\mathrm{aq}) \rightarrow 2 \mathrm{Mn}^{2+}(\mathrm{aq})+5 \mathrm{I}_{2}(\mathrm{aq})+8 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

The equation for the titration in Step 5 is shown.

2 S2O32−(aq)+I2(aq)→S4O62−(aq)+2I−(aq)2 \mathrm{~S}_{2} \mathrm{O}_{3}^{2-}(\mathrm{aq})+\mathrm{I}_{2}(\mathrm{aq}) \rightarrow \mathrm{S}_{4} \mathrm{O}_{6}^{2-}(\mathrm{aq})+2 \mathrm{I}^{-}(\mathrm{aq})

A student's results are shown.

Table for Question 3(b)(i) — Edexcel A-Level Chemistry AS

Plot a graph of volume of sodium thiosulfate against time.

Table for Question 3(b)(i) — Edexcel A-Level Chemistry AS