A-Level AQA Chemistry The Mole, Avogadro & The Ideal Gas Equation: 130 cm³ of oxygen and 40 cm³ of

130 cm³ of oxygen and 40 cm³ of nitrogen, each at 298 K and 100 kPa, were placed into an evacuated flask of volume 0.50 dm³ - AQA - A-Level Chemistry - Question 34 - 2017 - Paper 3

Question 34

130-cm³-of-oxygen-and-40-cm³-of-nitrogen,-each-at-298-K-and-100-kPa,-were-placed-into-an-evacuated-flask-of-volume-0.50-dm³-AQA-A-Level Chemistry-Question 34-2017-Paper 3.png

130 cm³ of oxygen and 40 cm³ of nitrogen, each at 298 K and 100 kPa, were placed into an evacuated flask of volume 0.50 dm³. What is the pressure of the gas mixture... show full transcript

Worked Solution & Example Answer:130 cm³ of oxygen and 40 cm³ of nitrogen, each at 298 K and 100 kPa, were placed into an evacuated flask of volume 0.50 dm³ - AQA - A-Level Chemistry - Question 34 - 2017 - Paper 3

Step 1

Calculate Total Moles of Gases

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Answer

To find the total pressure of the gas mixture, we first need to calculate the number of moles of each gas. Using the ideal gas law, we have:

For oxygen (O₂): $n_{O_2} = \frac{PV}{RT}$ Where:

P = 100 kPa = 100,000 Pa
V = 130 cm³ = 0.000130 m³
R = 8.314 J/(mol·K)
T = 298 K

Substituting the values gives: $n_{O_2} = \frac{100000 \times 0.000130}{8.314 \times 298} \approx 0.0050 \text{ moles}$

For nitrogen (N₂): $n_{N_2} = \frac{PV}{RT}$ Where:

P = 100 kPa = 100,000 Pa
V = 40 cm³ = 0.000040 m³

Thus, substituting: $n_{N_2} = \frac{100000 \times 0.000040}{8.314 \times 298} \approx 0.0016 \text{ moles}$

Step 2

Calculate Total Moles

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Answer

Total moles of the gas mixture: $n_{total} = n_{O_2} + n_{N_2} = 0.0050 + 0.0016 = 0.0066 \text{ moles}$

Step 3

Calculate Pressure in Flask

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Answer

Now, we want to find pressure in the flask at 298 K using volume of the flask (0.50 dm³ = 0.0005 m³):

Using the ideal gas law again: $P = \frac{nRT}{V}$ Where:

n = 0.0066 moles
R = 8.314 J/(mol·K)
T = 298 K
V = 0.0005 m³

Substituting the values: $P = \frac{0.0066 \times 8.314 \times 298}{0.0005} \approx 34.0 \text{ kPa}$

130 cm³ of oxygen and 40 cm³ of nitrogen, each at 298 K and 100 kPa, were placed into an evacuated flask of volume 0.50 dm³ - AQA - A-Level Chemistry - Question 34 - 2017 - Paper 3

Worked Solution & Example Answer:130 cm³ of oxygen and 40 cm³ of nitrogen, each at 298 K and 100 kPa, were placed into an evacuated flask of volume 0.50 dm³ - AQA - A-Level Chemistry - Question 34 - 2017 - Paper 3

Calculate Total Moles of Gases

Calculate Total Moles

Calculate Pressure in Flask

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