2. Atoms, molecules and stoichiometry
A section of Chemistry, 9701
Listing 10 of 208 questions
Explain what is meant by the term relative isotopic mass. A sample of copper contains two isotopes, 63Cu and 65Cu. The relative atomic mass of the copper in this sample is 63.55. Calculate the percentage abundance of each of these isotopes. Show your working.  percentage abundance of 63Cu = %  percentage abundance of 65Cu = %  Name the type of bonding within a sample of solid copper. Draw a labelled diagram to show the bonding within a sample of solid copper.  State the electronic configuration of a copper atom. 1s2 A student is provided with a sample of hydrated copper(sulfate, CuSO4•xH2O, and is asked to determine the value of x. The student dissolves a sample of the hydrated copper(sulfate in water and adds it to an excess of aqueous potassiumiodide to make a total volume of 250.0 cm3 of solution. 2CuSO4 + 4KI → 2CuI + I2 + K2SO4 The amount of iodine produced during this reaction is found by titrating a sample of this solution with sodiumthiosulfate solution. 25.0 cm3 of the iodine-containing solution requires 20.0 cm3 of 0.10 mol dm–3 sodiumthiosulfate solution. I2 + 2S2O3 2– → S4O6 2– + 2I– Calculate the amount, in mol, of copper(sulfate present in the original sample of hydrated copper(sulfate. Show your working.  amount of copper(sulfate = mol A total of 7.98 g of CuSO4 is present in 10.68 g of CuSO4•xH2O. Complete each row of the table to calculate the value of x, where x is an integer. [Mr: CuSO4,159.6] amount of CuSO4 in 10.68 g of CuSO4•xH2O mol amount of H2O in 10.68 g of CuSO4•xH2O mol value of x x =  
9701_s20_qp_23
THEORY
2020
Paper 2, Variant 3
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