A-Level Edexcel Chemistry questions with complete solutions

A-Level Edexcel Chemistry questions with complete solutionsAtomic Number number of protons in the nucleus of an atom of that element. Mass Number the sum of protons and neutrons in a nuclues of an atom Isotopes atoms of the same elementwith the same numberof protons but different nuber of neutrons Relative Atomic Mass the average mass of an atom of an element compared to a twelfth of the mass of an atom of carbon-12. Relative Isotopic Mass The mass of an atom of an isotope compared to one-twelfth of the mass of an atom of carbon-12 Quantum Shell the energy level of an electron. Orbital a region around the nucleus that can hold up to two electrons with opposite spins. What shape is the S orbital spherical What shape is the P orbital dumbell First Ionisation Energy the measure of energy is needed to completely remove one mole of electron from one mole of gaseous atom Second Ionisation Energy is a measure of energy needed to remove one-mole of electron from one mole of gaseous ion Periodicity A repeating trend in the properties of the elements across the periodic table Why are copper and chromium important? because they have a half-filled subshell. This gives added stability so minimises electron repulsion Why is the first ionisation energy the lowest? it is the lowest because the electron is further away from the nucleus so less attraction and more shielding by the inner electrons. This means less energy is needed to remove the electron. Why does ionisation energy increase as you go across the period? as you go across the periodic table there are more protons so more attraction to the electrons so decreasing atomic radii. This increases the ionisation energy. first ionisation energy for sodium see pic Why does ionisation energy increase from Na to Mg ionisation energy increases becasue magnesium has more protons so more attraction to the electron Why does ionisation energy decrease from Mg to Al because the electron being removed is from a new subshell. This means the electron is futher away from the nucleus so less attraction to the nucleus. Why does ionisation energy decrease from P to S There are more electrons in the same orbital so more repulsion. What is the trend in ionisation energy as you go down the period? As you go down periods the electros get further away from the nucleus and atomic radii increases. This means there is more shielding by inner electrons. Why does successive ionisation energy increase? because as you remove an electron the ratio of proton to electron increases. This means more attraction and so more energy needed to remove electrons. Explain the stages of mass spectrometer. Vapourisation- the sample is heated to produce gaseous atom. Ionisation- an electron gun is used to knock off electrons from the sample. Acceleration- the speed is increased to make deflection easier. Deflection- sample is deflected by electromagnet Detector- the sample is detected by detector. Why is fluorine the most reactive element because it has 7 protons which are pulling the electron so it is harder to lose electrons Decribe the trnd in reactivity as you go down group 1 as you go down group one Delocalised Electrons electrons that are not associated with any single atom or any single covalent bond. Metallic Bonding the electrostatic forces of attraction between the nuclei of metal cations and delocalised electrons. Polar Covalent Bond type of covalent bond between two atoms where the bonding electrons are unequally distributed. Because of this, one atoms carries a slight negative charge and the other a slight positive charge. Electronegativity the ability of an atom to attract a bonding pair of electrons Discrete (simple) Molecule an electrically neutral group of two or more atoms held together by chemical bonds. Displayed (full structural) Formula shows each bonding pair as a line drawn between the two atoms involved. Dipole said to exist when two charges of equal magnitude but opposite signs are separated by a small distance. Hydrogen Bond an intermolecular interaction (in which there is some evidence of bond formation) between a hydrogen atom of a molecule (or molecular fragment) bonded to an atom which is more electronegative than hydrogen and another atom in the same or a different molecule. Isoelectronic contains the same number of electrons Redox Reaction a reaction that involves both reduction and oxidation Oxidation the loss of electrons Reduction the gain of electrons Oxidising Agent a species that oxidises another species by removing one or more electrons. When an oxidising agent reacts it gains electrons and is, therefore, reduced. Reducing Agent a species that reduces another species by adding one or more electrons. When a reducing agent reacts it loses electrons, and is, therefore, oxidised. Oxidation Number the charge that an ion has or the charge that it would have if the species were fully ionic. Disproportionation the simultaneous oxidation and reduction of an element in a single reaction. Electromotive Force the standard electrode potential of a half cell (measured under standard conditions of 298 K, 100 kPa pressure and concentrations of 1 mol dm-3) connected to a standard hydrogen electrode. Basic Oxides are oxides of metals that react with water to form metal hydroxides, and with acids to form salts and water. Disproportionation the simultaneous oxidation and reduction of an element in a single reaction. Thermal Stability a measure of the extent to which a compound decomposes when heated. Transition Metal an element that forms one or more stable ions with incompletely filled d-orbitals. Ligand a species that uses a lone pair of electrons to form a dative bond with a metal ion. Complex a species containing a metal ion joined to ligands. Complex Ion a complex with an overall positive or negative charge. Coordination Number the number of dative bonds in the complex. Electromagnetic Spectrum the range of all wavelengths and frequencies of all the types of radiation. Complementary Colours are colours opposite each other on a colour wheel. Six Fold Coordination- refers to complexes in which there are six ligands forming coordinate bonds with the transition metal ion. Square Planar shape contains a central atom or ion surrounded by four atoms or ligands in the same plane and with bond angles of 90 degrees. Monodentate Ligand one that forms one dative bond with a metal ion. Bidentate Ligand one that forms two dative bonds with a metal ion. Multidentate Ligand one that forms several dative bonds with a metal ion. Amphoteric Behaviour refers to the ability of a species to reaction with both acids and bases. Heterogeneous Catalyst one that is in a different phase from the reactants. Adsorption the process that occurs when reactants form weak bonds with a solid catalyst. Desorption the process that occurs when products leave the surface of a solid catalyst. Homogeneous Catalyst one that is in the same phase as the reactants. Autocatalysis occurs when a reaction product acts as a catalyst for the reaction. Empirical Formula shows the smallest whole number ratio of atoms of each element in a compound. Molecular Formula shows the actual number of atoms of each element in a molecule. Molar Mass is the mass per mole of a substance. It has the symbol M and the units gmol-1. Mole is the amount of substance that contains the same number of particles as the number of carbon atoms in exactly 12g of the carbon-12 isotope. ... ... Avogadro Constant the number of atoms of carbon-12 in exactly 12g of carbon-12. Coefficients are the numbers written in front of species when balancing an equation. Spectator Ions are the ions in an ionic compound that do not take part in a reaction. Hydrates are compounds containing water of crystallisation, represented by formulae such as CuSO4.5H2O Avogadro's Law states that equal volumes of gases under the same conditions of temperature and pressure contain the same numbers of molecules. Molar Volume is the volume occupied by 1 mol of any gas. Solute a substance that is dissolved.