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Pearson Edexcel IAL Chemistry 1.10 Formula confirmation by experiment

Practise using experimental mass data and observations to confirm formulae and evaluate errors in simple oxide experiments.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
AS

Exam points

  • complete mass tables for copper oxide experiments to find masses of metal and oxygen
  • explain how incomplete reaction or reoxidation changes the calculated oxide formula

1.10—Determine a formula or confirm an equation by experiment question 1

[Maximum number: 4]

Precipitation reactions can be used to determine the formulae of compounds.
A bottle has a torn label which shows that it contains a nitrate with the formula X(NO_3)_2.

Figure for Question 1.10—Determine a formula or confirm an equation by experiment question 1 — Edexcel A-Level Chemistry AS

Procedure
- a technician dissolved a sample of 12.41 g of the nitrate in deionised water to make 100 cm^3 of solution
- the technician pipetted 5.0 cm^3 of 1.50 mol dm^-3 potassium iodide into each of a series of test tubes
- each test tube then had a volume of the nitrate solution added to it as shown in the table
- a cloudy yellow solution formed, and the precipitate was allowed to settle
- the height of the precipitate was then measured.

The equation for the reaction is

X(NO3)2(aq)+2KI(aq)→XI2( s)+2KNO3(aq)\mathrm{X}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+2 \mathrm{KI}(\mathrm{aq}) \rightarrow \mathrm{XI}_{2}(\mathrm{~s})+2 \mathrm{KNO}_{3}(\mathrm{aq})

The results of the experiment are shown.

Table for Question 1.10—Determine a formula or confirm an equation by experiment question 1 — Edexcel A-Level Chemistry AS

Identify X by using your answers to (b)(i), (b)(ii) and (b)(iii) to determine the M_r of the metal nitrate. You must show all your working.

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