BoardChemistry

States of Matter

2 Board Chemistry previous year questions on States of Matter — options free on every question; 1 include the answer & explanation free, the rest unlock with PYQ Pass.

Q1 FREE PREVIEW
PYQ

A closed vessel contains \(10\mathrm{g}\) of an ideal gas X at \(300\mathrm{K}\), which exerts \(2\mathrm{atm}\) pressure. At the same temperature, \(80\mathrm{g}\) of another ideal gas Y is added to it and the pressure becomes \(6\mathrm{atm}\). The ratio of root mean square velocities of X and Y at \(300\mathrm{K}\) is

[JEE Advanced 2024, Paper-1]

a

\(2\sqrt{2}∶\sqrt{3}\)

b

\(2\sqrt{2}∶1\)

c

\(1:2\)

d

\(2:1\)

✓ Correct answer: d)

\(2:1\)

Explanation

At constant V and T, P ∝ n.
Initial: P1 = 2 atm, moles of X = nX.
After adding Y: P2 = 6 atm, total moles = nX + nY.
(nX + nY)/nX = P2/P1 = 6/2 = 3 ⇒ nY = 2nX.

Given mX = 10 g, mY = 80 g.
Mx = 10/nX, My = 80/nY = 80/(2nX) = 40/nX ⇒ My = 4Mx.

u(rms) ∝ 1/√M, so uX/uY = √(My/Mx) = √4 = 2.
Ratio uX : uY = 2 : 1.

Q2
PYQ

1 L closed flask contains a mixture of 4 g of methane and 4.4 g of carbon dioxide. The pressure inside the flask at \({27}^{\mathrm{o}}\mathrm{C}\) is (Assume ideal behaviour of gases)

a

8.6 atm

b

2.2 atm

c

4.2 atm

d

6.1 atm

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