Question

determine the molar mass of freon - 11 gas if a sample weighing 0.597 g occupies 100. cm³ at 243°c, and 1,000. mmhg.
add your answer
integer, decimal, or e notation allowed
question 2
10 points
which gas has molecules with the greatest average molecular speed at 25°c?
a ch₄
b kr
c n₂
d ar

Explanation:

Step1: Convert units

• Convert pressure: \(P = 1000\ mmHg\times\frac{1\ atm}{760\ mmHg}\approx1.316\ atm\)
• Convert volume: \(V = 100\ cm^{3}=100\ mL = 0.1\ L\)
• Convert temperature: \(T=(243 + 273.15)\ K=516.15\ K\)
• Use the ideal - gas law \(PV=nRT\), and \(n=\frac{m}{M}\), so \(PV=\frac{m}{M}RT\), then \(M=\frac{mRT}{PV}\)
• \(R = 0.0821\ L\cdot atm\cdot K^{-1}\cdot mol^{-1}\), \(m = 0.597\ g\)

Step2: Calculate molar mass

Substitute the values into the formula \(M=\frac{mRT}{PV}\)

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for Question 2:
According to the formula for the root - mean - square speed \(u_{rms}=\sqrt{\frac{3RT}{M}}\) (where \(R\) is the gas constant, \(T\) is the temperature, and \(M\) is the molar mass of the gas). At a given temperature (\(T = 25^{\circ}C=(25 + 273)\ K = 298\ K\)), the gas with the smallest molar mass will have the greatest average molecular speed.

• Molar mass of \(CH_{4}\): \(M=(12 + 4\times1)\ g/mol=16\ g/mol\)
• Molar mass of \(Kr\): \(M = 83.8\ g/mol\)
• Molar mass of \(N_{2}\): \(M=(2\times14)\ g/mol = 28\ g/mol\)
• Molar mass of \(Ar\): \(M = 39.95\ g/mol\)

Since \(CH_{4}\) has the smallest molar mass among the given gases.

Answer:

192