7 a group of compounds called chlorofluorocarbons

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7. A group of compounds called chlorofluorocarbons have a wide range of uses but they also have harmful effects on the environment. State one: a) Use of chlorofluorocarbons (1 mark) b) Harmful effect of chlorofluorocarbons on the environments. (1 mark) 8. When 94.5g of hydrated barium hydroxide, Ba(OH) 2 .nH 2 O were heated to constant mass, 51.3g of anhydrous barium hydroxide were obtained. Determine the empirical formula of the hydrated barium hydroxide. (Ba = 137, O = 16, H = 1) (3 marks) 9. At 20 0 c, NO 2 and N 2 O 4 gases exist in equilibrium as shown in the equation below. 2NO 2(g) N 2 O 4(g); H = -ve Brown pale yellow State and explain the observation that would be made when; a) A syringe containing the mixture at 20 0 c is immersed in ice-cold water (1 ½ mks) b) The volume of the gaseous mixture in a syringe is reduced. (1 ½ mks) 10. Name the process which takes place when: a) Solid carbon (IV) oxide (dry ice) changes directly into gas (1 mark) 4
b) A red litmus paper turns white when dropped into chlorine water. (1 mark) c) Propene gas molecules are converted into a giant molecule (1 mark) 11. a) water from a town in Kenya is suspected to contain chloride ions but not sulphate ions. Describe how the presence of the chloride ions in the water can be shown. (1 mk) b) State one advantage of drinking hard water rather than soft water. (1 mk) 12. The table below shows the atomic masses and the percentage abundance of the isotopes L 1 and L 2 of element L. Use it to determine the relative atomic mass of element L. (3mks) Isotope Atomic mass % abundance L 1 62.93 69.09 L 2 64.93 30.91 13. The diagram below represents the set-up that was used to prepare and collect hydrogen chloride gas in the laboratory. 5
a) State the purpose of concentrated sulphuric (vi) acid in the wash bottle. (1 mark) b) Write an equation for the reaction between dry hydrogen chloride gas and heated iron. (1 mark) c) Hydrogen chloride gas is dissolved in water to make hydrochloric acid. State one use of hydrochloric acid. (1mk) 14. Below is a list of oxides. MgO, N 2 O, K 2 O, CaO, and Al 2 O 3 . Select: a) A neutral oxide (1 mk) b) A highly water soluble basic oxide (1 mark) c) An oxide which can react with both sodium hydroxide solution and dilute hydrochloric acid. (1 mk) 15. Study the standard reduction potential given and answer the questions that follow. (The letters are not the actual symbols of the elements).

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