45. Complete the following crossword puzzle (Fig. 3.1) by using the name of the chemical elements. Use the data given in Table 3.2.Table 3.2 Across 2. The element used by Rutherford during his α–scattering experiment 3. An element which forms rust on exposure to moist air 5. A very reactive non–metal stored under water 7. Zinc metal when treated with dilute hydrochloric acid produces a gas of this element which when tested with burning splinter produces a pop sound. Down 1. A white lustrous metal used for making ornaments and which tends to get tarnished black in the presence of moist air 4. Both brass and bronze are alloys of the element 6. The metal which exists in the liquid state at room temperature 8. An element with symbol Pb Fig. 3.1 46. (a) In this crossword puzzle (Fig 3.2), names of 11 elements are hidden. Symbols of these are given below. Complete the puzzle. 1.Cl 7. He 2.H 8.F 3.Ar 9. Kr 4.O 10. Rn 5.Xe 11. Ne 6. N EXEMPLAR PROBLEMS Fig. 3.2 (b) Identify the total number of inert gases, their names and symbols from this cross word puzzle. 47. Write the formulae for the following and calculate the molecular mass for each one of them. (a) Caustic potash (b) Baking powder (c) Lime stone (d) Caustic soda (e) Ethanol (f) Common salt 48. In photosynthesis, 6 molecules of carbon dioxide combine with an equal number of water molecules through a complex series of reactions to give a molecule of glucose having a molecular formula C6 H12 O6. How many grams of water would be required to produce 18 g of glucose? Compute the volume of water so consumed assuming the density of water to be 1 g cm–3. ATOMSAND MOLECULES

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