Q5 of 79 Page 3

By what processes do you concentrate the following ores:
i) PbS(galena)
ii) Fe2O3(haematite)
iii) Al2O3.2H2O (bauxite).

i) PbS (galena) is concentrated by froth floatation method.ii) Fe2O3 (haematite) is concentrated by magnetic separation.iii) Al2O3.2H2O (bauxite) is concentrated by leaching process (chemical method).

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3 Give reasons for the following
i) Zinc oxide is considered an amphoteric oxide.
ii) Non-metals in general do not displace hydrogen from dilute acids.
iii) Metals conduct electricity. 4 Identify the following oxides with neutral, acidic, basic and amphoteric oxides.
i) Al2O3  ii) MgO  iii) SO2  iv) CO;  v) Na2O  vi) N2O  vii) ZnO  viii) CO2  ix) SO3 x) CaO. 6 Why is that iron does not occur as a metal in the crust of the earth? What are the common compound forms in which iron occurs? Which of these is more often used for extracting iron? Why are carbon and limestone mixed with iron ore before feeding it into the blast furnace? Write the chemical equations for the reduction step and the slag formation step. 7 By what chemical processes do you obtain the following metals?
i) Mercury from HgO  ii) Iron from Fe2O3  iii) Manganese from MnO2  iv) Sodium form NaCl  v) Aluminium from Al2O3.