Calculate mole fractions and partial pressures.

In the subtopic Kp and partial pressure (A-level only), this AQA A-Level Chemistry 7405 learning objective focuses on calculate mole fractions and partial pressures. It belongs to Equilibrium constant Kp for homogeneous systems (A-level only), so revision should stay anchored to this exact subtopic rather than drifting into a generic GCSE-level chemistry summary. Approved keywords to use include mole fraction, partial pressure. Mole fraction. means the ratio of the number of moles of a specific component to the total number of moles of all components in a mixture Avoid the mistake of students often confuse the calculation of partial pressure with total pressure, leading to incorrect values; instead, 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 For exam answers, 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