JEE Main · 2025 · 07 Apr 2025 · Shift 1 · States of Matter

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At the sea level, the dry air mass percentage composition is given as nitrogen gas : 70.0 , oxygen gas : 27.0 and argon gas : 3.0. If total pressure is 1.15 atm , then calculate the ratio of followings respectively :

(i) partial pressure of nitrogen gas to partial pressure of oxygen gas

(ii) partial pressure of oxygen gas to partial pressure of argon gas

(Given : Molar mass of

N, O

and Ar are 14, 16, and

40 g mol^{- 1}

respectively)

(A) $4.26, 19.3$
(B) $2.59, 11.85$
(C)5.46, 17.8
(D) $2.96, 11.2$ ✓ Correct

Answer: (D)

Solution

Partial pressures stand in the ratio of the moles of each gas, and the moles follow from mass percentage divided by molar mass. With

M (N_{2}) = 28

M (O_{2}) = 32

and

M (A r) = 40

, the moles are

n_{N_{2}} = 70/28 = 2.5

n_{O_{2}} = 27/32 = 0.844

and

n_{A r} = 3/40 = 0.075

. Hence

P_{N_{2}} : P_{O_{2}} = 2.5/0.844 = 2.96

and

P_{O_{2}} : P_{A r} = 0.844/0.075 = 11.2

. The two ratios are 2.96 and 11.2.

JEE Main · 2025 · 07 Apr 2025 · Shift 1 · Single correct option

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JEE Main · 2025 · 07 Apr 2025 · Shift 1 · States of Matter

Solution

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