Question

. At what temperature will oxygen molecules
have same rms speed as helium molecules at
S.T.P.? (Molecular masses of oxygen and
helium are 32 and 4 respectively)
n.​

Answer 1

Explanation:

T

2

=273K,M

o1

(oxygen)=32×10

−3

kg/mol,

M

o2

(hydrogen)=4×10

−3

kg/mol,

v

rms

=

M

0

3RT

The rms speed of oxygen molecules, v

1

=

M

01

3RT

1

and that of helium molecules,

v

1

=

M

02

3RT

2

when v

1

=v

2

M

01

3RT

1

=

M

02

3RT

2

∴

M

01

T

1

=

M

02

T

2

∴ Temperature, T

1

=

M

02

M

01

.T

2

=

4×10

−3

(32×10

−3

)(273)

=2184K