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Atoms And Molecules
State drawbacks of Dalton’s atomic theory of matter.
Some of the drawbacks of Dalton’s atomic theory of matter are:
1. According to Dalton’s atomic theory, matter is indivisible, i.e., which cannot be divided. But now it is known that under special circumstances, atoms can be divided into still smaller particles called electrons, protons and neutrons.
2. Dalton’s atomic theory fails to explain why substances like charcoal, graphite and diamond have different properties when all these substances are made up of the same type of atoms, called carbon atoms.
3. Dalton’s atomic theory postulated that all the atoms of the same element have exactly the same mass. It is now known that isotopes are atoms of the same element but have different masses.
4. It is now known that some atoms called isobars have same masses but these belong to different elements. Whereas Dalton’s atomic theory says that atoms of different atoms have different mass.
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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 ?
What are the postulates of Dalton’s atomic theory of matter?
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