2024 a level paper 1

2024 a level paper 1 Before the first titration, the 25 cm3 pipette is rinsed with a small volume of the 0.100 mol dm-3 barium hydroxide solution. State why it is good practice to rinse the pipette in this way. - correct answersSo that the titration is done with known concentration of Ba(OH)2 Electrospray ionisation is used instead of electron impact for the ionisation of a protein in a mass spectrometry experiment. Suggest why. - correct answersthe protein (ion) does not break up/fragment Explain how the ions are detected in the TOF mass spectrometer. State how the relative abundance of the ions is determined. - correct answersM1 (Ions hit a detector/electron multiplier and) each ion gains an electron (generating a current) M2 current is proportional to abundance Explain why the enthalpy of hydration of fluoride ions is more negative than the enthalpy of hydration of chloride ions. - correct answersM1 F- has a higher charge density M2 stronger attraction (of fluoride ion) to δ+ on H/ electron deficient H (in water) Explain why the second ionisation energy of calcium is greater than the first ionisation energy of calcium. - correct answersElectron removed from a positive charge/ion Give an equation for the reaction between sulfur dioxide and water. - correct answersSO2 + H2O → H2SO3 Give an equation for the reaction of magnesium with steam. State one observation made. - correct answersM1 Mg + H2O → MgO + H2 M2 White solid/white powder OR (Bright) white light/white flame Give an equation to show how an excess of magnesium oxide reacts with phosphoric acid (H3PO4). - correct answers3MgO + 2H3PO4 → Mg3(PO4)2 + 3H2O Give the displayed formula for the anion formed when sulfur trioxide reacts with water. - correct answers Hydrochloric acid is added to the burette using