AQA 2023 AS CHEMISTRY 7404/2 Paper 2 Organic and Physical Chemistry questions and answers verified

AQA 2023 AS CHEMISTRY 7404/2 Paper 2 Organic and Physical Chemistry questions and answers verified What is the equation linking mass moles and MR? Mass=moles * MR What is the definition of Ar (relative atomic mass)? The average mass of an atom of an element compared to the mass of one twelfth of carbon 12. What does Mr stand for? Relative molecular mass Define relative isotopic mass. The mass of an isotope of an element compared to the mass of one twelfth of the mass of carbon 12 What is the relative mass of an electron? 1/1840 What is an isotope? Isotopes of an element are atoms worth the same number of protons but a different number of neutrons. Where does most of the volume of an atom come from The electron orbitals Describe the history of the atomic model including names and theories John Dalton: Atoms are indivisible spheres that make up different elements JJ.Thompson: Plum pudding model; Atoms are spheres of positive charge with negative electrons embedded in them Ernest Rutherford: Nuclear Model; Small positive nucleus sorrow dead b y 'cloud' of negative electrons. Niels Bohr: Nuclear model but improved by suggesting that electrons exist in shells of fixed energy. Explain How Ernest Rutherford came up with the nuclear model of the atom. He fired alpha particles at sheet of gold foil; most passed through unaffected which suggests an atom is mostly empty space. Some were deflected backwards which suggests a small nucleus with a very high charge density. Why did Niels Bohr improve upon the original nuclear model of the atom? If electrons existed in a 'cloud' then the electrons would spiral down into the nucleus causing it to collapse. Give three benefits of instrumental methods of analysis. More accurate, more sensitive and produce results more quickly than physical methods. Name the four stages of time of flight mass spectrometry 1. Ionisation 2. Acceleration 3. Flight tube 4. Detection. Name and explain the two methods of ionisation in time of flight mass spectrometry Electron Impact/electron ionisation: Sample is vaporised then high energy electrons are fired at it using an electron gun. The electron knocks another electron off of the atom causing it to ionise.THIS METHOD CAUSES FRAGMENTATION Electrospray ionisation::: sample dissolved in solvent and then passed through hyperdermic needle to give a fine mist. The tip of the needle is attached to the positive terminal of a high voltage supply. The particles are then ionised as they gain a proton from the high voltage supply (though remember gaining a proton affects the mass of the atom. What is an electron gun? (Used in ionisation by electron impact) A hot wire filament with a current running through it that emits electrons. How is stage 2 carried out in mass spectrometry? The ions are accelerated by passing them through a charged electric field When the particles move through the flight tube in time of flight mass spectrometry, do small particles or large particles travel faster and why? The smaller particles travel faster because all particles are given the same kinetic energy so using the formula KE=halfmv squared. The lower the mass the greater the velocity How are particles detected in stage 4 of time of flight mass spectrometry? The positive ions hit a negatively charged plate, the ions are then discharged by gaining an electron from the plate which generates a movement of electrons and thus a measurable electric current. The size of the current determines the number of ions hitting the plate at the time. A sample of magnesium produces a mass spectrum graph that has a peak at 24 measuring 79%, at 25 for 10% and at 26 for 11% what is the Ar of Magnesium. 24.32 A mass spectrum graph of propane is produced. Explain the small peaks at 45 and 46 They are produced because of molecular ions of propane with C13 and/or H2. How many electrons are in each electron orbital? 2 Describe the movement of electrons in each orbital. The electrons spin in opposite directions What is an electron orbital? An area of which an electron pair are LIKELY to be found. What is the order of the sub shells and how many orbitals are in each one? S - 1 P - 3 D -5 F - 7 Lowest energy shells generally fill first but what is the exception to that rule. And which element are an exception to the exception? The 4s shell fills before the 3d sub shell. Copper and chromium are different, only one electron goes into the 4s shell before the 3d shell starts to fill. What is the sub shell notation of calcium? 1s1 2s2 2p6 3s2 3p6 4s2 Which correctly shows the electron orbitals in oxygen? And why? [II] [II] [11][11][ ] OR [II] [II] [II][I ][I ] [II] [II] [II][I ][I ] Beacuse electrons fill each orbital BEFORE they share. What is the sub shell notation for Chromium? 1s2 2s2 2p6 3s2 3p6 4s1 3d5 When forming an ion, are electrons lost from the 4s shell or the 3d shell first? They are lost from the 4s shell first (which is what you expect unlike the filling of the sub shells) What is the sub shell notation for a scandium ion? 1s2 2s2 2p6 3s2 3p6 What is the definition of ionisation energy? The energy required to remove one electron form every atom in one mole of gaseous atoms What is the equation for the second ionisation of sodium? Na+(g) ——> Na2+ (g) + e - You must have the gas state symbol or else it isn't ionisation energy. How does first ionisation energy change as you go down a group and why? It decreases beacuse of a greater distance from the nucleus so weaker electrostatic attraction. Also more shielding from the inner electron shells as well as repulsion from those said electrons. These factors make it easier to remove an electron. How does the first ionisation energy change as you move across a period (from left to right) and why? It generally increases because there are more protons so a greater attraction from the nucleus and no extra electron shells so broadly the same amount of shielding. First ionisation energy generally increases across a Period but there are 2 exceptions. Explain why. The slight drop between group 2 and group 3 is because electrons are moving from the s sub shell to the p sub shell so there is some repulsion and shielding from the s sub shell making it easier to remove the electron. The slight drop between group 5 and g roup 6 is because this is when the electrons start to share orbitals so the electrons experience some repulsion from the other electron in its orbital making it easier to remove. Why does the is the second ionisation energy greater than the first? Because in second ionisation energy you are removing an electron from a positively charged ion so there will be a stronger attraction from the nucleus. Which group is this element in and why? * * * Ionisation energy * * *