重有一條THXXX - Ans.fyi 參考答案

重有一條THXXX

tze

2011-08-12 12:14 am

two identical glass containers X and Y each hold 1mole of gas.comtainer X is filled with hydrogen gas(molar mass=2g mol^-1) while container Y is filled with helium (molar mass 4G mol^-1),if the pressure in X and Y are the same which of the following statement is true
A temperature of the gas in X is higher than in Y
B temperature of the gas in Y is higher than in X
C the root mean squre speed of gas molecules in x is higher than in Y

Dthe root mean squre speed of gas molecules in x is lower than in Y

THXX

回答 (1)

天同

2011-08-12 1:38 am

✔ 最佳答案

The answer is option C.

From the ideal gas equation: PV = nRT
i.e. T = PV/nR
It is given that both containers are of the same volume (V) and the gas pressure (P) are the same, and they are filled with 1 mole of gas (hydrogen or helium), i.e. n =1. The temperature T for the two gases should be the same. Hence options A and B are wrong.

From the equation, pressure of gas P is given by
P = (1/3).d.c^2
where d is th gas density and c is the rems speed of gas molecules.

Becuase the presures of hydrogen and helium are the same
hence, (1/3).d(H).c(H)^2 = (1/3).d(He).c(He)^2
where d(H) and d(He) are the desnities of hydrogen and helium respectively,
and d(H) and d(He) are the corresponding densities.

i.e. c(H)^2/c(He)^2 = d(He)/d(H) > 1
because the density of helium is higher than that of hydrogen.
thus, c(H)^2 > c(He)^2
or c(H) > c(He)
The answer is therefore option C

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