DHS_H1_CHEM_P2 ANS

2 Section A 1 Antimony (Sb), with atomic number 51 has been known sinc e about 4000BC. Nowadays, its main use is to harden and to strengthen lead alloys. A typical sample of antimony consists of two isotopes and has the following composition by mass: 121Sb, 57.25%, 123Sb, 42.75%. (a) (i) Calculate the relative atomic mass of the antimony sample. Relative atomic mass = (57.25 x 121 + 42.75 x 123) / 100 = 121.9 (II) Define the term relative atomic mass. Relative mass of a particle (egs. atom, molecule, ion, etc.) is defined as the number of times the particle is heavier than the mass of an atom of carbon–12. [3] Antimony is produced in two-stage process from the sulphide ore, Sb2S3. The ore is first roasted in oxygen to form the oxide. 2Sb2S3(s) + 9O2(g)  Sb4O6(s) + 6SO2(g) The oxide is then reduced with carbon. Sb4O6(s) + 3C(s)  4Sb(s) + 3CO2(g) (b) Showing your working clearly, calculat e the volume of carbon dioxide at room temperature and pre ssure that would be produc ed by the processing of 3400 g of Sb2S3. 2 Sb2S3 = S4O6 = 3 CO2 No. of mol of CO2 = 3/2 x 3400/(340.1) = 15.0 mols Volume of CO2 = 15 x 24dm3 = 360 dm3 [3] [Total: 6 marks] [Turn Ove r

3 Section A [Turn Over 2 The figure shows a plot of first ionisation energy against atomic number for the elements of atomic number 10 to 18. (The letters are not the chemical symbols for the elements concerned.) (a) Write an equation to define the first ionization energy of A. A(g)  A+(g) + e [1] (b) (i) Describe the general trend of the ionization energies from B to I as shown in the graph above. The successive I.E. from B to I generally increases. Nuclear charge increases when electrons are removed and there are stronger electrostatic forces of attraction between nucleus and valence electrons. Therefore more energy is required to remove the remaining electrons. [2] A First ionization energy / kJ mol-1 F I H C G E D B Atomic number (ii) Explain briefly why the first ionization energy of D is less than C. The first i onisation energy of D involves the removal of a 3p electron whereas first I.E of C involves the removal of a 3s electron. Smaller amount of energy is r equired to remove the 3p electron in D which is

4 further from the nucleus than 3s electron in C. [2] (b) Draw the shape of the orbital from which electron is lost when (i) Element B forms a singly charged ion, (ii) Element H forms a singly charged ion. [2] (c) Give the full electronic configuration of the element labeled F. 1s 22s22p63s23p3 [1] [Total:8 marks] 3 Each of these elem ents in Period 3 will react with oxygen given suitab