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Atoms And Molecules
What are the differences between the mass of an object and its weight?
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Differences between mass and weight: |
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Mass |
Weight |
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1. Mass is the quantity of matter contained in a body and is the measure of its inertia. 2. Its value remains constant at all places. 3. It is a scalar quantity. 4. It is measured by a pan balance. 5. Mass of a body is never zero. 6. Its unit is kg. |
1. Weight of a body is the force with which a body is attracted towards the centre of the earth. 2. Its value (W = mg) changes from place to place due to the change in the value of acceleration due to gravity ‘g’. 3. It is a vector quantity. 4. It is measured by a spring balance. 5. Weight of a body is zero at the centre of the earth because there ‘g’ becomes zero. 6. Its unit is newton or kg-wt. |
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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.
50 g of 10% lead nitrate is mixed with 50 g of 10% sodium chloride in a closed vessel. After the reaction has taken place, it was found that 6.83 g of lead chloride was precipitated. Besides, the reaction mixture contained 90 g water and sodium nitrate. Calculate the amount of sodium nitrate formed.
Name and explain two important laws of chemical combination ?
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