Chemistry Class-11: Chapter – 1. Some Basic Concepts of Chemistry – Part-7 (For CBSE, ICSE, IAS, NET, NRA 2022)

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VI. Long Answer Type

Question: 42

A vessel contains of dioxygen at pressure) . The gas is now transferred to another vessel at constant temperature, where pressure becomes half of the original pressure. Calculate

(i) Volume of the new vessel.

(ii) Number of molecules of dioxygen.


Hence, of oxygen will occupy,

According to Boyle՚s law:

(ii) Number of molecules of oxygen in the vessel

Question: 43

Calcium carbonate reacts with aqueous to give and according to the reaction given below:

What mass of will be formed when of reacts with of ? Name the limiting reagent. Calculate the number of moles of formed in the reaction.


Number of moles of

Number of moles of

According to given equation 1 mol of (s) requires of . Hence, for the reaction of mol of number of moles of required would be:

But we have only , hence, is limiting reagent. So amount of formed will depend on the amount of available. Since, forms mol of , therefore, of would give:


Question: 44

Define the law of multiple proportions. Explain it with two examples. How does this law point to the existence of atoms?


Question: 45

A box contains some identical red coloured balls, labelled as A, each weighing grams. Another box contains identical blue coloured balls, labelled as B, each weighing grams. Consider the combinations , , and and show that law of multiple proportions is applicable.


(Hint : Show that the masses of B which combine with the fixed mass of A in different combinations are related to each other by simple whole numbers) .