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Equilibrium constant Kp for homogeneous systems (A-level only)

This A-level-only topic applies equilibrium constants to gaseous systems.

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90 min

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AQAA LevelChemistryPhysical chemistry

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5 objective pages available

Kp and partial pressure (A-level only)5 objectives

partial pressuremole fractionKp expressionKpequilibrium position

Understanding Partial Pressure: Explain clearly by remember that the partial pressure of a gas in a mixture is the pressure that gas would exert if it occupied the entire volume alone. Link the point to Kp and partial pressure (A-level only), then state the evidence, calculation, mechanism, observation, or conclusion required by the question.
Calculating Partial Pressure: Explain clearly by to find the partial pressure of a gas in a mixture, use the formula: P = (n/V)RT, where P is the partial pressure, n is the number of moles of the gas, V is the volume of the gas mixture, R is the ideal gas constant, and T is the temperature in Kelvin. Link the point to Kp and partial pressure (A-level only), then state the evidence, calculation, mechanism, observation, or conclusion required by the question.

Misunderstanding Partial Pressure: To define partial pressure in a gas mixture, use the formula: P_partial = X * P_total, where P_partial is the partial pressure of the gas, X is the mole fraction of the gas, and P_total is the total pressure of the gas mixture. For example, if the total pressure is 2 atm and the mole fraction of gas A is 0.3, then P_partial = 0.3 * 2 atm = 0.6 atm. Thus, the partial pressure of gas A is 0.6 atm. Keep the correction anchored to Kp and partial pressure (A-level only) and the objective: Define partial pressure in a gas mixture.
Incorrect Calculation of Partial Pressure: To calculate the partial pressure of a gas in a mixture, use the formula: P_partial = X_gas * P_total, where X_gas is the mole fraction of the gas. For example, if the mole fraction of gas A is 0.3 and the total pressure is 100 kPa, then P_partial = 0.3 * 100 kPa = 30 kPa. Ensure to clearly identify the mole fraction and total pressure before performing the calculation. Keep the correction anchored to Kp and partial pressure (A-level only) and the objective: Calculate mole fractions and partial pressures.

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