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CIE Nov 2015 v2 Paper 5 Q1
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![PMT It is possible to determine the relative molecular mass, Mr, of a small sample of a volatile liquid by measuring its mass and then heating to vaporise it to obtain its volume as a gas. (a) Explain how the relative molecular mass can be determined in this way.[2] (b) (i) The volume of the vaporised sample depends on its temperature and pressure. In an experiment, a sample of volatile liquid of known mass was vaporised and its volume recorded. The pressure was correctly recorded as 101 kPa but the temperature was incorrectly recorded as 50 C. The correct temperature was 60 C. By considering the effect of these different temperatures on the gas volume, explain how the value of the calculated Mr would be affected.[3] (ii) The temperature was maintained at 60 C but the pressure was increased to 110 kPa. Would this have given an answer that was nearer to the true value of the relative molecular mass? Explain your answer.[1]UCLES 2015 9701/52/O/N/15<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v2_QP_-_Paper_5_CIE_Chemistry_A-level_1.jpg)
![Page 2 Mark Scheme Syllabus Paper Cambridge International A LevelOctober/November 2015 9701 52 Expected Answer Mark Question (a) PV = nRT Mr = mass / amount in mol OR formulae correctly re-arranged Mr = m / n OR g / n OR any of these (b) (i) volume (measured / recorded at 60 C) is higher OR volume is lower at 50 C / at lower temperature (calculated) Mr is lower (ii) The volume would be reduced OR as P increases Mr increases AND answer closer to the true value / yes (c) Place water / oil / sand within the outer VM tube AND heat the outer tube Shows appropriate connections to collect the air over water / in syringe (any size) using the side tube (d) Hexane: is (in)flammable / burns readily (cid:127) (cid:127) causes irritation to the skin (cid:127) causes breathing difficulties (cid:127) forms explosive mixture (with air) OR is combustible Any one from the list above (e) (i) The air expands (And) goes into the collection apparatus (ii) (Wait until) no more bubbles (of air are produced) in the water / syringe no longer moves (f) The mass of tube + hexane and mass of empty tube Temperature and pressure Syringe reading before hexane is added + the syringe reading after hexane is added [1] [1] [3] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] Qn1 [Total: 15]Cambridge International Examinations 2015<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v2_MS_-_Paper_5_CIE_Chemistry_A-level_1.jpg)