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Atoms And Molecules
Question
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How do you account for the fact that gram atomic mass or gram molecular mass of any substance contains the same number of particles?

Answer

Atomic mass of any substance indicates the times it is heavier than 1/12th of C-12 atom. Now atomic mass of H atom is one u, it means that one C-12 atom is 12 times as heavy as one H atom or to say 1000 C-12 atoms are 12 times as heavy as 1000 H atoms or 6.023 x 1023 C-12 atoms (12 grams C-12 are found to contain 6.023 x 1023 atoms) are 12 times as heavy as 6.023 x 1023 H atoms. Since atomic mass of C-12 is 12 u and that of H atom is 1 u, it can be inferred that weight equal to atomic mass of C-12 or H atom contains the same number of atoms. Thus, it can be shown that gram atomic mass or gram molecular mass of all substances have the same number, i.e., 6.023 x 1023 particles.

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Some More Questions From Atoms And Molecules Chapter

What are polyatomic ions? Give examples.

Write the chemical formulae of the following:

(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.