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Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them. (You may use appendix-III).
- Ammonia
- Carbon monoxide
- (Hydrogen chloride
- Aluminium fluoride
- Magnesium sulphide
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Complete the following crossword puzzle (Fig. 3.1) by using the name of the chemical elements. Use the data given in Table.
| Across | Down | ||
| 2 | The element used by Rutherford during his α–scattering experiment | 1 | A white lustrous metal used for making ornaments and which tends to get tarnished black in the presence of moist air |
| 3 | An element which forms rust on exposure to moist air | 4 | Both brass and bronze are alloys of the element |
| 5 | A very reactive non–metal stored under water | 6 | The metal which exists in the liquid state at room temperature |
| 6 | Zinc metal when treated with dilute hydrochloric acid produces a gas of this element which when tested with burning splinter produces a pop sound. | 8 | An element with symbol Pb |
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Which of the tubes in Fig. 2.1 (a) and (b) will be more effective as a condenser in the distillation apparatus?
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Find out the wrong statement from the following
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Which one of the following fish is a surface feeder?
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Preventive and control measures adopted for the storage of grains include
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Farming without the use of chemicals such as fertilizers, herbicides and pesticides is known as ______.
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Differentiate between the following
Capture fishery and Culture fishery
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Give the merits and demerits of fish culture?
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What do you understand by composite fish culture?
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Play a game for writing formula.
Example 1: Make placards with symbols and valencies of the elements separately. Each student should hold two placards, one with the symbol in the right hand and the other with the valency in the left hand. Keeping the symbols in place, students should criss-cross their valencies to form the formula of a compound.
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Play a game for writing formula.
Example 2: A low-cost model for writing formulae: Take empty blister packs of medicines. Cut them in groups according to the valency of the element, as shown in the figure. Now, you can make formulae by fixing one type of ion into other.
For example:
The formula for sodium sulphate:
2 sodium ions can be fixed on one sulphate ion.
Hence, the formula will be Na2SO4.
Do it yourself:
Now, write the formula of sodium phosphate.
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Calculate the molecular mass of H2.
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Calculate the molecular mass of O2.
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Calculate the molecular mass of Cl2.
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Calculate the molecular mass of CO2.
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Calculate the molecular mass of CH4.
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Calculate the molecular mass of C2H6.
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Calculate the molecular mass of C2H4.
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Calculate the molecular mass of NH3.
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