Chemistry Advanced Subsidiary PAPER 1: Core Inorganic and Physical Chemistry., Pearson Edexcel Level 3 GCE. GRADED A+

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Some questions must be answered with a cross in a box . If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . 1 Bromine exists as two stabl... e isotopes. The two isotopes are represented by the symbols 35 79Br and 35 81Br. (a) Give one similarity and one difference between these two isotopes by referring to the number of particles in the nuclei of the two isotopes. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (b) The relative abundance of the two isotopes in a sample cannot be found in a chemical test. (i) Give the reason why, despite the difference in atomic structure, the isotopes have the same chemical reactions. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) State how the relative abundance of the two isotopes can be found. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... ....................................................................................................................................................................................................................................................................................*P67083A0324* Turn over 3 (c) (i) Complete the electronic configuration of a bromine atom. (1) 1s2 2s2 .............................................................................................................................................................................................. (ii) What is the number of electrons in the fourth quantum shell of bromine? (1) A 2 B 7 C 17 D 18 (Total for Question 1 = 7 marks (b) 25.0 cm3 portions of the standard solution described in (a) are titrated with hydrochloric acid solution of concentration 0.300 mol dm–3, using methyl orange as an indicator. The table shows the results for this titration. Titration 1 Titration 2 Titration 3 Final volume / cm3 30.25 29.75 31.25 Initial volume / cm3 0.30 0.90 2.60 Total titre / cm3 29.95 28.85 28.65 (i) What is the colour change at the end-point of the reaction? (1) From To A red orange B red yellow C yellow orange D yellow red (ii) State why the value for the total titre in Titration 1 should not be used to calculate the mean titre. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (iii) Calculate the mean titre [Show More]

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