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Edexcel Jan 2016 (IAL) Paper 2 Q22
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![Mark Acceptable Answers Reject Just all the product is useful Just all the reactants become products No product wasted (It is an) addition reaction OR An addition polymer is made OR All the reactants are made into the desired / required product OR Only one product (is made) OR No waste products / no by-products ALLOW No side products Question Number 22 (b)<br />
Reject Mark Acceptable Answers First markM1: (Position of equilibrium shifts/favours) to the left OR to the reactants OR to the backward reaction/direction OR to the reverse reaction/direction OR towards C3H6 / NH3 / O2 ALLOW decreases yield of products / decreases yield of CH2CHCN / decreases yield of H2O (1) Second markM2: This mark is dependent on the correct change in THE position of equilibrium (i.e. (0) overall for question if states that eqm shifts to the RIGHT) (Forward) reaction is exothermic OR (Forward) reaction gives out heat OR Backward reaction is endothermic / takes in heat OR Reverse reaction is endothermic / takes in heat IGNORE References to just decreasing the temperature / opposes the increase in temperature (1) Additional comment JUST a statement that it moves in / favours the endothermic direction can get M1 ONLY IF M2 has already been awarded (as it is then clear that the candidate realises that from right to left is the endothermic direction). Question Number 22 *(c)(i)<br />
Mark Acceptable Answers Reject References to ATOMS/PARTICLES, if chooses to refer to these, (instead of molecules) no 2nd mark First markM1: (Position of equilibrium shifts/favours) to the left OR to the reactants OR to the backward reaction/direction OR to the reverse reaction/direction OR towards C3H6 / NH3 / O2 ALLOW decreases yield of products / decreases yield of CH2CHCN / decreases yield of H2O (1) Second markM2: This mark is dependent on the correct change in THE position of equilibrium (i.e. (0) overall for question if states that eqm shifts to the RIGHT) Right-hand side has more moles/molecules (of gas) OR Products have more moles/molecules (of gas) OR Left-hand side has fewer moles/molecules (of gas) OR Reactants have fewer moles/molecules (of gas) NOTE: 2nd mark awarded if mentions: 3 moles/molecules (of gas) on LHS and 4 moles/molecules (of gas) on RHS (1) Question Number 22 *(c)(ii)<br />
Acceptable Answers Question Number 22 (d)(i) (y-axis:) Fraction of molecules / Reject atoms instead of molecules/particles Mark number of molecules ALLOW Proportion of molecules ALLOW particles instead of molecules for the label on the y-axis and (x-axis:) Energy / E / kinetic energy NOTE: BOTH graphs axes (on p14 and p15 of script) need to be labelled correctly for this mark<br />
Mark Reject Ea shown at peak or to the left of peak More atoms Acceptable Answers Question Number *22 (d)(ii) First markM1: Correct drawing of Maxwell-Boltzmann distribution at T2 clearly identified NOTE As long as it is clear which curve the candidate has drawn, if it is correctly drawn award this mark, even if their curve is not actually labelled T2 NOTE Peak of candidates curve (at the higher temperature) should be clearly lower and to the right of that at the lower temperature (1) Second markM2: Suitable Ea shown on graph (1) Third markM3: (At higher temperature) more molecules/more collisions / more particles have energy greater than the activation energy NOTE: Must refer to activation energy / Ea for M3 IGNORE more frequent collisions (1) Number of molecules T2 Ea Only M1 can be awarded if two Ea values drawn on graph for this part<br />
Acceptable Answers Reject Mark First markM1: Ea for the catalysed reaction shown to the left of Ea for the un-catalysed reaction NOTE Do not penalise again the actual position of either Ea if M2 was not awarded in Q22(d)(ii) for the same reason (1) Second markM2: EITHER (With catalyst) more molecules / more collisions / more particles have energy greater than the (new, lower) activation energy OR Diagram labelled as shown below NOTE If a shaded area is shown between the two Ea lines, even if it is unlabelled, award M2 NOTE ALLOW alternatives for M2 such as More molecules have enough energy to react (with the catalyst) OR More molecules are able to react at lower energies (with the catalyst) [Unlike in Q22(d)(i), Ea doesnt HAVE to be mentioned.] (1) Two curves shown (no M1) More atoms Number of molecules Energy/E more molecules with energy above the new, lower Ea cat IGNORE Just a statement that a catalyst provides an alternative reaction route/pathway of lower activation energy (Total for Question 22 = 14 marks) Question Number 22 *(d)(iii)<br />](https://learnah.org/wp-content/uploads/2018/08/January_2016_IAL_MS_-_Unit_2_Edexcel_Chemistry_A-level_22-0.jpg)
