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JEE Main 20262 AprilEvening Shift
Exam
JEE Main
Year
2026
Date
2 April
Shift
Evening Shift
Subject
Physics
Chapter
Kinetic Theory of Gases

JEE Main 2026 · 2 April · Evening Shift · Physics · Kinetic Theory of Gases

A mixture of carbon dioxide and oxygen has volume 8310 cm ^3 ,...

A mixture of carbon dioxide and oxygen has volume 83108310 cm3^3, temperature 300300 K, pressure 100100 kPa and mass 13.213.2 g. The number of moles of carbon dioxide and oxygen gases in the mixture respectively are _______.
(Assume both carbon dioxide and oxygen gases behave like ideal gases) [R=8.31[R = 8.31 J/mol.K]]

Options

  1. A0.150.15 and 0.180.18
  2. B0.250.25 and 0.080.08
  3. C0.210.21 and 0.120.12
  4. D0.130.13 and 0.200.20

Correct answer

C. 0.210.21 and 0.120.12

Step-by-step solution

Using the ideal gas equation, the total number of moles of the mixture is given by:

n=PVRTn = \dfrac{PV}{RT}

Substituting the given values:
P=100 kPa=105 PaP = 100 \text{ kPa} = 10^5 \text{ Pa}
V=8310 cm3=8.31×10−3 m3V = 8310 \text{ cm}^3 = 8.31 \times 10^{-3} \text{ m}^3
T=300 KT = 300 \text{ K}
R=8.31 J/(mol⋅K)R = 8.31 \text{ J/(mol}\cdot\text{K)}

n=105×8.31×10−38.31×300=100300=13 moln = \dfrac{10^5 \times 8.31 \times 10^{-3}}{8.31 \times 300} = \dfrac{100}{300} = \dfrac{1}{3} \text{ mol}

Let n1n_1 and n2n_2 be the number of moles of CO2CO_2 and O2O_2 respectively.

n1+n2=13n_1 + n_2 = \dfrac{1}{3}

The total mass of the mixture is 13.2 g13.2 \text{ g}. Using the molar masses of CO2CO_2 (44 g/mol44 \text{ g/mol})andO2and O_2 (32 g/mol32 \text{ g/mol}):

44n1+32n2=13.244n_1 + 32n_2 = 13.2

Substituting n2=13−n1n_2 = \dfrac{1}{3} - n_1 into the mass equation:

44n1+32(13−n1)=13.244n_1 + 32\left(\dfrac{1}{3} - n_1\right) = 13.2

12n1+323=13.212n_1 + \dfrac{32}{3} = 13.2

12n1=39.6−323=7.6312n_1 = \dfrac{39.6 - 32}{3} = \dfrac{7.6}{3}

n1=7.636=1990≈0.21 moln_1 = \dfrac{7.6}{36} = \dfrac{19}{90} \approx 0.21 \text{ mol}

The number of moles of O2O_2 is:

n2=13−1990=1190≈0.12 moln_2 = \dfrac{1}{3} - \dfrac{19}{90} = \dfrac{11}{90} \approx 0.12 \text{ mol}

The number of moles of CO2CO_2 and O2O_2 are 0.210.21 and 0.120.12 respectively.

Answer: 0.210.21 and 0.120.12
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