0 . 553 g of a boron-hydrogen compound created a pressure of 0 . 658 atm in a bulb of 407 mL at 100 ° C . Analysis showed it to be 85 . 7 % boron. Calculate its molecular formula.

For boron and hydrogen compound, given, Pressure = P = 0 . 658 atm Volume = V = 407 ml ∴ V = 407 1000 litre V = 0 . 407 litre Temperature = T = 100 ° C T = 100 + 273 T = 373 K . Mass of boron and hydrogen = 0 . 553 gm . Universal gas constant = R = 0 . 0821 . Molecular mass M = 63 . 45 gm , Out of this, mass 85 . 7 % is boron 14 . 3 % is hydrogen. ∴ Applying ideal gas equation, PV = nRT n = W MW 0 . 658 × 407 1000 = 0 . 553 M × 0 . 0821 × 373 M = 63 . 23 . ∴ 63 . 23 gm compound has = 85 . 7 × 63 . 23 100 g of boron ∴ = 54 . 31 gm of ' B ' ∴ = 54 . 31 10 . 8 g atom of ' B ' ≈ 5 . 028 gm atom of ' B ' ≈ 5 gm atom of ' B ' . Now, formula becomes B 5 H x ∴ 5 × 10 . 8 + x = 63 . 23 MW of B = 10 . 8 x = 63 . 23 - 54 x = 9 . 23 x ≈ 9 . Hence, molecular formula of compound is B 5 H 9 .

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Important Questions on States of Matter

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 4 - States of Matter>DPP 4.2>Q 1

What should be the percentage increase in pressure for a

5 %

decrease in volume of a gas at constant temperature?

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IMPORTANT

Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 4 - States of Matter>DPP 4.2>Q 2

The pressure exerted by

12 g

of an ideal gas at temperature

t ° C

in a vessel of volume

V

litre is one

atm

. When the temperature is increased by

10

degree at the same volume, the pressure increases by

10 %

. Calculate the temperature

t

and volume

V

. (Molar mass of the gas

= 120

HARD

JEE Main

IMPORTANT

Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 4 - States of Matter>DPP 4.2>Q 3

0.553 g

of a boron-hydrogen compound created a pressure of

0.658 atm

in a bulb of

407 mL

100 ° C

. Analysis showed it to be

85.7 %

boron. Calculate its molecular formula.

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JEE Main

IMPORTANT

Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 4 - States of Matter>DPP 4.2>Q 4

Calculate the

%

of 'free volume' available in

1 mol

gaseous water at

1.0 atm

and

100 ° C

. Density of liquid water at

100 ° C

0.958 g / mol

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 4 - States of Matter>DPP 4.2>Q 5

A mixture of ${NH}_{3} (g)$ and $N_{2} H_{4} (g)$ is placed in a sealed container at $300 K$ . The pressure within the container is $0.6 atm$ . The container is heated to $1000 K$ where, the two gases undergo decomposition reactions.

$2 {NH}_{3} (g) \to N_{2} (g) + 3 H_{2} (g)$ and $N_{2} H_{4} (g) \to N_{2} (g) + 2 H_{2} (g)$

The pressure of the container at this stage become $4.8 atm$ . What was the mole percent of ${NH}_{3} (g)$ in the original mixture?

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 4 - States of Matter>DPP 4.2>Q 6

10 ° C

, the density of a fixed mass of an ideal gas divided by its pressure is

X

. At

110 ° C

, this ratio would be:

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 4 - States of Matter>DPP 4.2>Q 7

Which of these gases exhibits behavior that deviates most significantly from that expected from an ideal gas?

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 4 - States of Matter>DPP 4.2>Q 8

Ten moles of an ideal gas is filled in a closed vessel. The vessel has cylinder and piston type arrangement and pressure of the gas remains constant at

0.821 atm

. Which of the following graph represents the correct variation of

\log V

\log T

? (

V =

Volume in litre and

T =

Temperature in kelvin)

Which of the following plots is/are correct?

Important Questions on States of Matter

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