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CIE Nov 2013 v5 Paper 3 Q2
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![Examiners For Use The formula of hydrated iron(II) sulfate is FeSO4.xH2O where x shows the number of moles of water of crystallisation. The value of x can be found by heating solid hydrated iron(II) sulfate to remove the water of crystallisation. FA 3 is hydrated iron(II) sulfate, FeSO4.xH2O. (a) Method Record all weighings, in an appropriate form, in the space below.Weigh and record the mass of the empty crucible. Tip the contents of the tube labelled FA 3 into the weighed crucible. Reweigh and record the mass of the crucible and FA 3. Use a pipe-clay triangle to support the crucible and contents on a tripod. Heat gently for about three minutes. Leave the crucible to cool for approximately five minutes. While you are waiting for the crucible to cool, start work on Question 3.When cool, reweigh the crucible with the residue. Reheat gently for three minutes, cool and reweigh the crucible until you are satisfied that all the water of crystallisation has been lost. It should not be necessary to reheat the crucible more than three times. II III IV VI [6]UCLES 2013 9701/35/O/N/13 [Turn over<br />
Examiners For Use (b) (i) Calculate the mass of water lost and the mass of anhydrous iron(II) sulfate that remains after the heating process. mass of water lost =g mass of anhydrous iron(II) sulfate =g (ii) Determine the value of x in the formula of hydrated iron(II) sulfate, FeSO4.xH2O. (Ar : H, 1.0; O, 16.0; S, 32.1; Fe, 55.8) value of x =[3] (c) A group of students carried out this practical and made their measurements correctly. The students calculated a value of 9 for x. The textbook value of x is less than 9. (i) Suggest an error in the practical procedure of the experiment that could account for this result and explain why this gives a value of x that is too high.(ii) Suggest a modi cation that could be made to the experimental procedure to reduce this error. Explain why this modi cation should give an answer for x that is closer to the textbook value.[3] [Total: 12]UCLES 2013 9701/35/O/N/13<br />](https://learnah.org/wp-content/uploads/2018/08/November_2013_v5_QP_-_Paper_3_CIE_Chemistry_A-level_2-0.jpg)
![Page 5 Mark Scheme Syllabus Paper GCE A LEVELOctober/November 2013 9701 35 Question Sections Indicative material Mark (a) PDO I Records at least four different balance readings Layout (including 2 after heating) in the correct space. PDO II Gives all appropriate headings and units for all Recording weighings. III All recorded balance readings consistent to at least 1 decimal place. MMO IV Evidence of reheating to constant mass. Quality For balances reading to 1 dp two masses must be identical. For 2 or 3 dp balances, two masses must be within 0.05 g. V and VI Examiner calculates to 3 significant mass residue of mass water figures. Award V and VI for a difference from Supervisor up to 0.10. Award V for a difference 0.10 <0.30. (b) (i) ACE I Calculation of mass of water and iron(II) sulfate Interpretation (ii) PDO Display ACE II Mrs of 18 and 151.9 / sum of Ars if correctly used III Calculation x = mass water151.9 mass FeSO418 (or 8.439 / ratio used for Q) and [6] Interpretation final answer to nearest integer. [3]Cambridge International Examinations 2013<br />](https://learnah.org/wp-content/uploads/2018/08/November_2013_v5_MS_-_Paper_3_CIE_Chemistry_A-level_2.jpg)