Atoms And Molecules
What do you mean by weight of an object on the moon ? Why is the weight of an object on the moon is less than that on the earth?
The force with which the object is attracted towards the centre of the moon is the weight of an object on the moon.
The mass and radius of the moon is less than that of the earth. Due to this the moon exerts lesser force of attraction on the object. Hence, the weight of an object on the moon is less than that on the earth.
The gravitational force of the moon is about one sixth of that on the earth.
Example. Suppose the weight of a certain object is 6 kg-wt on the earth. If the same object is weighed on the moon, then the weight will be just 1 kg-wt.
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What are polyatomic ions? Give examples.
(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate
(d) Aluminium chloride
(e) Calcium carbonate
Give the names of the elements in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Calculate the molar mass of the following substances:
(a) Ethylene
(b) Sulphur molecule, S8
(c) Phosphorus molecule, P4
(d) Hydrochloric acid, HCl
(e) Nitric acid, HNO3.
What is the mass of:
(a) 1 mole of nitrogen atoms
(b) 4 moles of aluminium atoms
(c) 10 moles of sodium sulphite.
Convert into mole
(a) 12 gm of oxygen gas
(b) 20 gm of water
(c) 22 gm of carbon dioxide.
What is the mass of?
(a) 0.2 mole oxygen atoms.
(b) 0.5 mole of water molecules.
Calculate the number of molecules of sulphur (S8) present in 16 gm of solid sulphur.
Calculate the number of aluminium ions present in 0.56 gm of aluminium oxide.
Explain law of conservation of mass.
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