Question

plz 50 points and brainliest but give me the true answer with steps
At 200 K, the molecules or atoms of an unknown gas, X, have an average velocity equal to that of Ar atoms at 400 K. What is X? (Assume ideal behavior.)
A) He
B) CO
C) HF
D) HBr
E) F2​

Answer 1

Answer:

i think A...  

Explanation:

Answer 2

The unknown gas with the same average velocity as atoms of argon is hydrogen fluoride (HF).

The given parameters;

• temperature of the gas, = 200 K
• temperature of the argon = 400 K
• atomic mass of argon = 40 g/mol

The average speed of an atom at a given temperature and mass is calculated as follows;

$\bar V = \sqrt{\frac{8RT}{\pi M} } \\\\\bar V_{Ar} = \bar V _{X}\\\\\sqrt{\frac{8RT_{Ar}}{\pi M_{Ar}} } = \sqrt{\frac{8RT_{X}}{\pi M_{X}} } \\\\\frac{8RT_{Ar}}{\pi M_{Ar}} = \frac{8RT_{X}}{\pi M_{X}}\\\\\frac{T_{Ar}}{M_{Ar}} = \frac{T_{X}}{M_{X}}\\\\M_ X = \frac{T_ XM_{Ar}}{T_{Ar}} \\\\M_X = \frac{200 \times 40}{400} \\\\M_ X= 20 \ g/mol$

The molar mass of hydrogen fluoride is calculated as;

HF = 1 + 19 = 20 g/mol

Thus, the unknown gas with the same average velocity as atoms of argon is hydrogen fluoride (HF).

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