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Compare the rms speed of hydrogen molecules at 127°C with rms speed of oxygen molecules at 27ºC given that molecular masses of hydrogen and oxygen are 2 and 32 respectively.

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Question

Compare the rms speed of hydrogen molecules at 127°C with rms speed of oxygen molecules at 27ºC given that molecular masses of hydrogen and oxygen are 2 and 32 respectively.

Numerical
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Solution

Data: M01 (hydrogen) = 2 g/mol

M02 (oxygen) = 32 g/mol

T1 (hydrogen) = 273 + 127 = 400 K

T2 (oxygen) = 273 + 27 = 300 K

The r.m.s. speed, `(v_(r.m.s.)) = sqrt((3 R T)/M_0)`,

Where M0 denotes the molar mass.

∴ `(v_(r.m.s._1) ("hydrogen"))/(v_(r.m.s._2) ("oxygen")) = sqrt((T_1/T_2)(M_02/M_01))`

= `sqrt((400/300)(32/2))`

= `sqrt((4/3)(16))`

= `((2)(4))/sqrt3`

= `8/sqrt3`

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Chapter 3: Kinetic Theory of Gases and Radiation - Exercises [Page 74]

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Balbharati Physics [English] Standard 12 Maharashtra State Board
Chapter 3 Kinetic Theory of Gases and Radiation
Exercises | Q 16 | Page 74

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