A 385 cm³ sample of carbon dioxide at 100 kPa and 25 °C was mixed with 2.89 × 10⁻² mol of argon - AQA - A-Level Chemistry - Question 28 - 2017 - Paper 3
Question 28
A 385 cm³ sample of carbon dioxide at 100 kPa and 25 °C was mixed with 2.89 × 10⁻² mol of argon. The gas constant, R = 8.31 J K⁻¹ mol⁻¹
What is the mole fraction of... show full transcript
Worked Solution & Example Answer:A 385 cm³ sample of carbon dioxide at 100 kPa and 25 °C was mixed with 2.89 × 10⁻² mol of argon - AQA - A-Level Chemistry - Question 28 - 2017 - Paper 3
Step 1
Calculate the number of moles of carbon dioxide
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Answer
To find the number of moles of CO₂, we can use the ideal gas law formula:
n=RTPV
Where:
P = pressure in atm = ( \frac{100 , kPa}{101.325 , kPa/atm} \approx 0.9867 , atm )
V = volume in liters = ( \frac{385 , cm^3}{1000} = 0.385 , L )
R = 0.0821 L·atm/(K·mol)
T = temperature in Kelvin = 25 + 273.15 = 298.15 K
Now substituting in the values:
n=0.0821L⋅atm/(K⋅mol)×298.15K0.9867atm×0.385L≈0.015mol
Step 2
Calculate the total number of moles in the mixture
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Answer
The total moles, ( n_{total} ), is the sum of the moles of CO₂ and argon:
