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Atoms And Molecules

Question

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Explain law of conservation of mass.

Solution

Law of consveration of mass state that mass can neither be created nor be destroy in chemical reaction. For example, take a solution of lead nitrate in water. Weigh it. Let it be x gm. Then add a given amount of solution (y gm) of sodium chloride. It will be found that a white precipitate is formed. Weigh the total solution. It will be found that total weight of the contents is (x + y) gm, i.e., equal to the total weight of the two solutions taken. Hence, it can be inferred that mass is neither created nor lost even during a chemical change. Similar results are obtained when any other chemical reaction has taken place. Only care to be taken is that no material is allowed to escape during the reaction.

Some More Questions From Atoms And Molecules Chapter

When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen ? Which law of chemical combination will govern your answer?

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.

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