Use measured masses and stoichiometric ratios to confirm an empirical or hydrate formula, then explain how incomplete reaction, reoxidation or residual water affects the result.
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.
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
The results of the experiment are shown.
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.