chemistry question paper solve it class 10
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1. (a) phosphorus
2. (c) aluminum (Al)
3. (a) calcium
4. The major limitations of Newlands' law of octaves were : (i) It was applicable to only lighter elements having atomic masses upto 40 u, i.e., upto calcium. ... (ii) It was assumed that only 63 elements existed in nature and no new elements would be discovered in the future
5. i) When zinc is added to the solution of iron sulphate, the colour of iron sulphate solution changes. It is because zinc is more reactive than iron, therefore, it displaces iron from its solution of iron sulphate and a grey precipitate of iron and a colourless solution of zinc sulphate is formed.
6.Sodium is a highly reactive metal and reacts vigorously with the oxygen, carbon dioxide and moisture present in the air such that it may even cause a fire. To prevent this explosive reaction, Sodium is kept immersed in kerosene because Sodium doesn't react with kerosene.
7. Hydrogen gas
hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal.
when iron react with dilute H2SO4
it forms iron sulphate and liberate hydrogen gas
Fe + H2SO4》 FeSO4 + H2
8. (a) mercury
Generally all the metals are found in the solid state at room temperature. The exception to this is mercury. Mercury is found in liquid state at room temperature. Whereas non metals are found in the 3 states at room temperature i.e. solid, liquid and gas.
(b) Mendeleevs Periodic Law: Properties of elements are the periodic function of their atomic masses. Achievements:i It could classify all the elements discovered at that time. ii It helped in the discovery of new elements. iii it helped in the correction of the atomic mass of some of the elements.