AQA A-LEVEL CHEMISTRY 7405/1 INORGANIC AND PHYSICAL CHEMISTRY MARKING SCHEME JUNE 2021 VERSION: 2.0 FINAL.

For example, in a question requiring 2 answers for 2 marks: Correct answers Incorrect answers (ie incorrect rather than neutral) Mark (2) Comment 1 0 1 1 1 1 They have not exceeded the maximum number of responses so there is no penalty. 1 2 0 They have exceeded the maximum number of responses so the extra incorrect response cancels the correct one. 2 0 2 2 1 1 2 2 0 3 0 2 The maximum mark is 2 3 1 1 The incorrect response cancels out one of the two correct responses that gained credit. 3 2 0 Two incorrect responses cancel out the two marks gained. 3 3 0 Marking procedure for calculations Full marks should be awarded for a correct numerical answer, without any working shown, unless the question states ‘Show your working’ or ‘justify your answer’. In this case, the mark scheme will clearly indicate what is required to gain full credit. If an answer to a calculation is incorrect and working is shown, process mark(s) can usually be gained by correct substitution / working and this is shown in the ‘Comments’ column or by each stage of a longer calculation. Errors carried forward, consequential marking and arithmetic errors Allowances for errors carried forward are most likely to be restricted to calculation questions and should be shown by the abbreviation ECF or consequential in the marking scheme. An arithmetic error should be penalised for one mark only unless otherwise amplified in the marking scheme. Arithmetic errors may arise from a slip in a calculation or from an incorrect transfer of a numerical value from data given in a question. Equations In questions requiring students to write equations, state symbols are generally ignored unless otherwise stated in the ‘Comments’ column. AQA A-level CHEMISTRY 7405/1 Paper 1 Inorganic and Physical Chemistry Mark scheme June 2021 Version: 1.0 Final Examiners should also credit correct equations using multiples and fractions unless otherwise stated in the ‘Comments’ column. Oxidation states In general, the sign for an oxidation state will be assumed to be positive unless specifically shown to be negative. Interpretation of ‘it’ Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the correct subject. Phonetic spelling The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical term or if the question requires correct IUPAC nomenclature. Brackets (…..) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the sense of the answer required. Ignore / Insufficient / Do not allow Ignore or insufficient is used when the information given is irrelevant to the question or not enough to gain the marking point. Any further correct amplification could gain the marking point. Do not allow means that this is a wrong answer which, even if the correct answer is given, will still mean that the mark is not awarded. Marking crossed out work Crossed out work that has not been replaced should be marked as if it were not crossed out, if possible. Where crossed out work has been replaced, the replacement work and not the crossed out work should be marked. Reagents The command word ‘Identify’, allows the student to choose to use either the name or the formula of a reagent in their answer. In some circumstances, the list principle may apply when both the name and the formula are used. Specific details will be given in mark schemes. The guiding principle is that a reagent is a chemical which can be taken out of a bottle or container. Failure to identify complete reagents will be penalised, but follow-on marks (eg for a subsequent equation or observation) can be scored from an incorrect attempt (possibly an incomplete reagent) at the correct reagent. Specific details will be given in mark schemes. For example, no credit would be given for: AQA A-level CHEMISTRY 7405/1 Paper 1 Inorganic and Physical Chemistry Mark scheme June 2021 Version: 1.0 Final  the cyanide ion or CN– when the reagent should be potassium cyanide or KCN;  the hydroxide ion or OH– when the reagent should be sodium hydroxide or NaOH;  the Ag(NH ) + ion when the reagent should be Tollens’ reagent (or ammoniacal silver nitrate). In this example, no credit is given for the ion, but credit could be given for a correct observation following on from the use of the ion. Specific details will be given in mark schemes. In the event that a student provides, for example, both KCN and cyanide ion, it would be usual to ignore the reference to the cyanide ion (because this is not contradictory) and credit the KCN. Specific details will be given in mark schemes.