Skip to content
CIE Nov 2014 v3 Paper 5 Q1
Answers available below
Show answer
Question
1
2
![The enthalpy change, Hr, for the reaction between magnesium atoms and aluminium ions to produce magnesium ions and aluminium atoms cannot be determined directly. However both metals react with dilute sulfuric acid and, using the enthalpy changes for these reactions, it is possible to use Hess Law to determine Hr. PMT You are to plan experiments that will enable you to determine the value of the enthalpy change for the reaction of 1 mol of magnesium with excess aqueous aluminium ions. You are provided with:0.30 g of magnesium ribbon, 0.30 g of aluminium foil, 1.00 mol dm3 sulfuric acid, standard laboratory equipment. (a)Write an equation for the reaction of magnesium and sulfuric acid.Write an equation for the reaction of aluminium and sulfuric acid.[2] (b) For the experiment to measure the enthalpy change when magnesium reacts with sulfuric acid name: (i) the independent variable,[1] (ii) the dependent variable.[1]UCLES 2014 9701/53/O/N/14<br />
(c) In the experiment, 20.0 cm3 of 1.00 mol dm3 sulfuric acid is used with 0.30 g of magnesium. (i) Calculate the minimum volume in cm3 of sulfuric acid required to react completely with 0.30 g of magnesium. [Ar: Mg, 24.3] PMT (ii) Suggest why 20.0 cm3 of sulfuric acid is used.[1] [1] (d) You are also provided with 0.30 g of aluminium. Calculate the minimum volume of 1.00 mol dm3 sulfuric acid required to react completely with 0.30 g of aluminium. [Ar: Al, 27.0] [2]UCLES 2014 9701/53/O/N/14 [Turn over<br />
PMT (e) Explain how you would carry out the experiment using the 0.30 g magnesium. (i) List the measurements you would make.[1] (ii) How would you do the experiment to make sure the results obtained would be as accurate as possible?[1] (iii) How would you use the measurements made in the experiment to determine the enthalpy change of the reaction between 1 mol of magnesium and sulfuric acid?[2]UCLES 2014 9701/53/O/N/14<br />
PMT (f) Write an ionic equation for the reaction between magnesium and aqueous aluminium ions. If the enthalpy change of the reaction between magnesium and sulfuric acid is H1 and that for aluminium and sulfuric acid is H2, use Hess Law to determine the enthalpy change, Hr, for the reaction between magnesium and aqueous aluminium ions. Then determine the enthalpy change for 1 mol of magnesium in terms of Hr.[3] [Total: 15]UCLES 2014 9701/53/O/N/14 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2014_v3_QP_-_Paper_5_CIE_Chemistry_A-level_1-0.jpg)
![Page 2 Mark Scheme Syllabus Paper Cambridge International A LevelOctober/November 2014 9701 53 Question Expected Answer Additional Guidance Mark (a) (i) (ii) (b) (i) (ii) (c) (i) (ii) (d) Mg + H2SO4 MgSO4 + H2 2Al + 3H2SO4 Al2(SO4)3 + 3H2 The mass of magnesium The temperature change 12.35 cm3 ECF equation in (a) The sulfuric acid must be in excess OR to ensure all the Mg has reacted / disappeared / dissolved / is the limiting reagent mol of Al = 0.011 (mol) AND mol of sulfuric acid = 0.0167 (mol) Volume of sulfuric acid =16.67 cm3 (e) (i) The volume / mass of sulfuric acid / solution OR a stated volume of sulfuric acid. AND The initial / start temperature (of the acid) AND The final / end temperature (reached by the acid) (ii) Insulate (the reaction mixture) OR Stir (the mixture while the reaction is taking place)Cambridge International Examinations 2014 1 1 1 1 1 1 1 1 [2] [1] [1] [1] [1] [2] [1] [1]<br />
Page 3 Mark Scheme Syllabus Paper Cambridge International A LevelOctober/November 2014 9701 53 Question Expected Answer Additional Guidance Mark (iii) Calculate the heat produced in the reaction using (f) (Q=) mc T Convert to 1 mol 3Mg + 2Al3+ 3Mg2+ + 2Al (Hr = ) 3H11H2 Or a suitable Hess Law cycle Hr 3Mg + 2Al3+ 3Mg2+ + 2Al 1H2 3H1 3Mg + 2Al Hr/3 1 1 1 1 1 [2] [3]Cambridge International Examinations 2014<br />](https://learnah.org/wp-content/uploads/2018/08/November_2014_v3_MS_-_Paper_5_CIE_Chemistry_A-level_1-0.jpg)
