past papers questions chemistry - November 2020 AS paper 1, 2017 paper 2 A level, paper 1 2019 A level Questions and Answers 100% Pass | Updated 2024

past papers questions chemistry - November 2020 AS paper 1, 2017 paper 2 A level, paper 1 2019 A level Questions and Answers 100% Pass | Updated 2024 This question is about atomic structure.There is a general trend for an increase in ionisation energy across Period 3. Give one example of an element that deviates from this trend. Explain why this deviation occurs. - Correct Answer ️️ -Aluminium / Al(Outer) electron in (3)p orbital / sub-shell (level) (3p) higher in energy / slightly more shielded (than 3s) / slightly further away (than 3s) Give an equation, including state symbols, to represent the process that occurs when the third ionisation energy of sodium is measured. - Correct Answer ️️ - Na2+(g)→Na3+(g) + e− This question is about a titration. A student dissolves an unknown mass of sodium hydroxide in water to make 200 cm3 of an aqueous solution. A 25.0 cm3 sample of this sodium hydroxide solution is placed in a conical flask and is titrated with 0.150 mol dm-3 sulfuric acid. The equation for this reaction is shown. 2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l) Table 1 shows the results of the titrations. (check paper for table - November 2020 as paper 1) Calculate the mass of sodium hydroxide used to make the original solution. - Correct Answer ️️ -Volume of H2SO4= (19.60 + 19.55) / 2 = (19.575 cm3 / 19.58 cm3) moles of H2SO4 = concentration x volume = 0.150 x (19.575 / 1000) (= 2.936 x 10-3 mol) Moles of NaOH in 25 cm3 = 2.936 x 10-3 x 2 = 5.87 x 10^-3mol moles of NaOH in original 200cm3 = 5.87 x 10^-3 x 8 = (= 0.04698 mol) Mass of NaOH = Mr x moles = 40.0 x 0.04698 = 1.88 g (1.9 g) The student uses a funnel to fill the burette with sulfuric acid before starting the titration. After filling, the student forgets to remove the funnel from the top of the burette. Suggest why this might affect the titre volume recorded. - Correct Answer ️️ - Additional drops of solution could have entered the burette from the funnel, (making the value on the burette lower). State one advantage of using a conical flask rather than a beaker for the titration. - Correct Answer ️️ -Less chance of splashing/losing any solution using a conical flask (when swirling) In a TOF mass spectrometer, ions are accelerated to the same kinetic energy (KE). The kinetic energy of an ion is given by the equation KE = 12 mv2 Where:KE = kinetic energy / J m = mass / kgv = speed / ms-1 In a TOF mass spectrometer, each 84Kr+ ion is accelerated to a kinetic energy of 4.83 × 10−16 J and the time of flight is 1.72 × 10−5 s Calculate the length, in metres, of the TOF flight tube. The Avogadro constant, L = 6.022 × 1023 mol−1 - Correct Answer ️️ -m = (84/1000)/6.022 x 10^23 = 1.395 x 10^- 25kg v^2 = 2ke/m =2x(4.83×10−16)/(1.395x10-25) v = √() = 83214.97 d =v x t= 83214.97 x 1.72 × 10−5 = 1.43 (m) A student determines the enthalpy change for the reaction between