Question

Which of the following statements is incorrect based on the graph?

X, Y, Z can be different gases or the same gas at different temperatures.

• A. X = He, Y = Ne, Z = Ar at 323 K
• B. He is plotted at X = 1000 K, Y = 500 K, Z = 100 K
• C. X, Y, Z have RMS speeds marked
• D. $T_c$ of gases is X>Y>Z

Answer 1

Answer: (A), (B), (C)

X, Y, Z have RMS speeds marked

a) At any given temperature T, $\text{molecular speed}\propto \sqrt{\frac{1}{M}}$
Mass of the gases follows the order: $Ar>Ne>He$
So the right inswer can be X = Ar, Y = Ne, Z = He at 323 K.

b) For a given gas, $\text{molecular speed}\propto \sqrt{T}$
As $T\uparrow es,c\uparrow es$
Correct order should be: $X>Y>Z$

c) Most probable speeds are marked on the graph.
Let say 1, 2 and 3 are maxima of the graph X, Y and Z respectively. For that slop is zero, i.e. $\frac{d\left(f\right(c\left)\right)}{dc}=0$
That is not rms.

d) As mass increases, intermolecular forced increases hence $T_c$ increases.