NCERT Class 11 Part 1 - Chemistry

J.V. Narlikar

Chapter 5

States of Matter - all with Video Answers

Educators

Chapter Questions

Problem 1

What will be the minimum pressure required to compress $500 \mathrm{dm}^{3}$ of air at 1 bar to $200 \mathrm{dm}^{3}$ at $30^{\circ} \mathrm{C} ?$

Ajay Singhal

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Problem 2

A vessel of $120 \mathrm{~mL}$ capacity contains a certain amount of gas at $35^{\circ} \mathrm{C}$ and $1.2$ bar pressure. The gas is transferred to another vessel of volume $180 \mathrm{~mL}$ at $35^{\circ} \mathrm{C}$. What would be its pressure?

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Problem 3

Using the equation of state $p V=n \mathrm{R} T$, show that at a given temperature density of a gas is proportional to gas pressure $p$.

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Problem 4

At $0^{\circ} \mathrm{C}$, the density of a certain oxide of a gas at 2 bar is same as that of dinitrogen at 5 bar. What is the molecular mass of the oxide?

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Problem 5

Pressure of 1 g of an ideal gas $A$ at $27^{\circ} \mathrm{C}$ is found to be 2 bar. When $2 \mathrm{~g}$ of another ideal gas $\mathrm{B}$ is introduced in the same flask at same temperature the pressure becomes 3 bar. Find a relationship between their molecular masses.

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Problem 6

The drain cleaner, Drainex contains small bits of aluminum which react with caustic soda to produce dihydrogen. What volume of dihydrogen at $20^{\circ} \mathrm{C}$ and one bar will be released when $0.15 \mathrm{~g}$ of aluminum reacts?

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Problem 7

What will be the pressure exerted by a mixture of $3.2 \mathrm{~g}$ of methane and $4.4 \mathrm{~g}$ of carbon dioxide contained in a $9 \mathrm{dm}^{3}$ flask at $27^{\circ} \mathrm{C}$ ?

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Problem 8

What will be the pressure of the $\mathrm{L}$ mxture when $0.5 \mathrm{~L}$ of $\mathrm{H}_{2}$ at $0.8$ bar and 2.0 L of dioxygen at $0.7$ bar are introduced in a $1 \mathrm{~L}$ vessel at $27^{\circ} \mathrm{C} ?$

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Problem 9

Density of a gas is found to be $5.46 \mathrm{~g} / \mathrm{dm}^{3}$ at $27^{\circ} \mathrm{C}$ at 2 bar pressure. What will be its density at STP?

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Problem 10

$34.05 \mathrm{~mL}$ of phosphorus vapour weighs $0.0625 \mathrm{~g}$ at $546^{\circ} \mathrm{C}$ and $0.1$ bar pressure. What is the molar mass of phosphorus?

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Problem 11

A student forgot to add the reaction mixture to the round bottomed flask at $27^{\circ} \mathrm{C}$ but instead he/she placed the flask on the flame. After a lapse of time, he realized his mistake, and using a pyrometer he found the temperature of the flask was 477 ${ }^{\circ} \mathrm{C}$. What fraction of air would have been expelled out?

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Problem 12

Calculate the temperature of $4.0$ mol of a gas occupying $5 \mathrm{dm}^{3}$ at $3.32$ bar. $\left(\mathrm{R}=0.083\right.$ bar $\mathrm{dm}^{3} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ ).

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Problem 13

Calculate the total number of electrons present in $1.4 \mathrm{~g}$ of dinitrogen gas.

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Problem 14

How much time would it take to distribute one Avogadro number of wheat grains, if $10^{10}$ grains are distributed each second ?

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Problem 15

Calculate the total pressure in a mixture of $8 \mathrm{~g}$ of dioxygen and $4 \mathrm{~g}$ of dihydrogen confined in a vessel of $1 \mathrm{dm}^{3}$ at $27^{\circ} \mathrm{C} . \mathrm{R}=0.083$ bar $\mathrm{dm}^{3} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$.

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Problem 16

Pay load is defined as the difference between the mass of displaced air and the mass of the balloon. Calculate the pay load when a balloon of radius $10 \mathrm{~m}$, mass $100 \mathrm{~kg}$ is filled with helium at $1.66$ bar at $27^{\circ} \mathrm{C}$. (Density of air $=1.2 \mathrm{~kg} \mathrm{~m}^{-3}$ and $\mathrm{R}=0.083$ bar $\mathrm{dm}^{3} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ ).

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Problem 17

Calculate the volume occupied by $8.8 \mathrm{~g}$ of $\mathrm{CO}_{2}$ at $31.1^{\circ} \mathrm{C}$ and 1 bar pressure. $\mathrm{R}=0.083$ bar $\mathrm{L} \mathrm{K}^{-1} \mathrm{~mol}^{-1}$

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Problem 18

$2.9 \mathrm{~g}$ of a gas at $95^{\circ} \mathrm{C}$ occupied the same volume as $0.184 \mathrm{~g}$ of dihydrogen at $17^{\circ} \mathrm{C}$, at the same pressure. What is the molar mass of the gas?

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Problem 19

A mixture of dihydrogen and dioxygen at one bar pressure contains $20 \%$ by weight of dihydrogen. Calculate the partial pressure of dihydrogen.

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Problem 20

What would be the SI unit for the quantity $p V^{2} T^{2} / n ?$

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Problem 21

In terms of Charles' law explain why $-273{ }^{\circ} \mathrm{C}$ is the lowest possible temperature.

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Problem 22

Critical temperature for carbon dioxide and methane are $31.1{ }^{\circ} \mathrm{C}$ and $-81.9^{\circ} \mathrm{C}$ respectively. Which of these has stronger intermolecular forces and why?

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Problem 23

Explain the physical significance of van der Waals parameters.

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