Inorganic Chemistry: Periodicity Exam With 100% Correct Answers 2024

Inorganic Chemistry: Periodicity Exam With 100% Correct Answers 2024 Which one of the following statements is correct? A The first ionisation energies of the elements in Period 3 show a general decrease from sodium to chlorine. B The electronegativities of Group 2 elements decrease from magnesium to barium. C The strength of the intermolecular forces increases from hydrogen fluoride to hydrogen chloride. D The ability of a halide ion to act as a reducing agent decreases from fluoride to iodide. B State the meaning of the term electronegativity. (a) Ability (or power) of an atom to attract electron density(or electrons or -ve charge) (1) in a covalent bond (1) or shared pairIf remove an electron lose first mark State and explain the trend in electronegativity values across Period 3 from sodium to chlorine. Trend: increases (1)Explanation: nuclear charge (number of protons) increases (1)electrons in same shell (1) OR similar shielding OR atoms similar size or smaller OR 1 mol of e- What is meant by the term first ionisation energy? Heat / enthalpy / energy for removal of one electron (1)from a gaseous atom (1)can score in an equation must have first mark to score the second The diagram below shows the variation in first ionisation energy across Period 3. (i) What is the maximum number of electrons that can be accommodated in an s sub-level? 2 What evidence from the diagram supports your answer to part (d)(i)? Two elements (or Na / Mg) before the drop (in energy) to Al (1) What evidence from the diagram supports the fact that the 3p sub-level is higher in energy than the 3s? ionisation energy of Al < that for Mg (1) What evidence from the diagram supports the fact that no more than three unpaired electrons can be accommodated in the 3p sub-level? fall in energy from P to S (1) or discontinuity in trend From Al to P there are 3 additional electrons (1) or three elements For second mark idea of block of 3 elements (a) P and Q are oxides of Period 3 elements. Oxide P is a solid with a high melting point. It does not conduct electricity when solid but does conduct when molten or when dissolved in water. Oxide P reacts with water forming a solution with a high pH. Oxide Q is a colourless gas at room temperature. It dissolves in water to give a solution with a low pH. (i) Identify P. State the type of bonding present in P and explain its electrical conductivity. Write an equation for the reaction of P with water. (a) (i) Deductions: Ionic (1) Ions not free to move in the solid state (1) Ions free to move when molten or in aqueous solution (1) Identity of P: Na2O or sodium oxide (1) N.B. If a formula given this must be correct Equation: Na2O + H2O → 2 NaOH (1) Identify Q. State the type of bonding present in Q and explain why it is a gas at room temperature. Write an equation for the reaction of Q with water Deductions: Covalent Intermolecular forces are weak or van der Waals forces,or dipole-dipole N.B. Any answer including a reference to hydrogen bonding is incorrect Identity of Q: SO2 or sulphur dioxide (1) Equation: SO2 + H2O → H2 SO3(1) NB Allow max one for SO3 R is a hydroxide of a Period 3 element. It is insoluble in water but dissolves in both aqueous sodium hydroxide and aqueous sulphuric acid. (i) Give the name used to describe this behaviour of the hydroxide. Amphoteric Write equations for the reactions occurring. Equation with NaOH Al(OH)3 + NaOH → NaAl(OH)4 OR Al(OH)3(H2O)3 + OH– → [Al(OH)4(H2O)2]– + H2OOR Al(OH)3 + OH– → [Al(OH)4]– R identified as Al(OH)3 or Al(OH)3(H2O)3 (1)A balanced equation (1) N.B. Allow equation with six co-ordinate Aluminium and up to six OH– ligandsN.B. Allow equation mark if M(OH)3 given in a balanced equation Equation with H2SO4 2Al(OH)3 + 3H2SO4 → Al2(SO4)3 + 6H2O OR Al(OH)3(H2O)3 + H+ → [Al(OH)2(H2O)4+ + H2O NB Allow equations with six co-ordinate Aluminium and up to six H2O ligands NB Allow equation mark if M(OH)3 given in a balanced equation Correct Al species as product (1)A balanced equation (1) Suggest why R is insoluble in water.