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Atoms And Molecules
State the contribution of Dalton’s atomic theory to the mass of atom. What steps were taken to resolve this issue?
Dalton’s atomic theory states that each atom has a characteristic mass and all atoms of an element are identical. Since, the mass of an atom is very very small, it was a difficult task to determine the mass of an individual atom. Therefore, it was decided to measure the atomic mass of an atom. Atomic mass is the relative atomic mass of an atom as compoared to some particular atom. For example, carbon and oxygen combine to form carbon monoxide. It is observed that 3 g of carbon combines with 4 g of oxygen. In other words.
carbon is 4/3 times its mass of oxygen, since, oxygen combines with a large number of elements, oxygen atom was taken as standard and 1/16 of mass of oxygen was taken as one atomic mass unit (u).
Now a days 1/12 of the mass of C-12 isotope of carbon is taken as the standard reference for measuring atomic masses.
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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?
Hydrogen and oxygen combine in two different ways to produce water and hydrogen peroxide. Which of Dalton’s law does this observation confirm? Explain.
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