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MOLE CONCEPT AND STIOTIOMETRY TEST 1 Total 20 marks 40 min Question 1 (3 marks) When heated, potassium permanganate decomposes according to the following equation: 2KMnO4 K2MnO4 + MnO2 + O2 Some potassium permanganate was heated in a test tube. After collecting one litre of oxygen at room temperature, it was found that the test-tube had undergone a loss in mass of 1.32 g. If one litre of hydrogen under the same condition of temperature and pressure has a mass of 0.0825 g, calculate the relative molecular mass of oxygen. Question 2 (1 + 1 + 1 = 3 marks) a. State Avogadro s law. b. Define molar volume. c. The mass of 5.6 L of certain gas is 12 g. What is the relative molecular mass. Question 3 ( 3 marks) A metal M forms a volatile chloride containing 65.5% chlorine. If the density of the chloride relative to hydrogen is 162.5, find the molecular formula of the chloride. (M = 56, Cl = 35.5). Question 4 (2 + 2 = 4 marks) The equations given below relate to the manufacture of sodium carbonate. (i) NaCl + NH3 + CO2 + H2O NaHCO3 + NH4Cl (ii) 2NaHCO3 Na2CO3 + H2O + CO2. (a) What mass of sodium hydrogen carbonate must be heated to give 21.2 g of sodium carbonate. [Molecular weight of Na = 14, H = 1, C = 12 and O = 16). (b) To produce the mass of sodium hydrogen carbonate calculated in (a), what volume of carbon dioxide, measured at s.t.p., would be required.
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