2021 P1 Q8 - Describing Dalton's Law

Let Chemistry Guru, Singapore's top choice for JC Chemistry tuition, guide you through 2021 A Levels H2 Chemistry Paper 1 Question 8.

We want to determine which of the following descriptions of Dalton's Law is correct.

Statement A - Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

This statement describes Avogadro's Law instead, where volume of gas is proportionate to the number of moles of gas at constant temperature and pressure.

Statement B - Partial pressure of a gas in a mixture is given by the product of its mole fraction and the total pressure.

This statement is true and related to Dalton's Law. However this is more application rather than the definition of Dalton's Law so let's see if there is a better answer.

Statement C - Partial pressure of a gas in a mixture is given by the product of its percent by mass and the total pressure.

This statement is not describing any gas law hence it is false.

Statement D - Total pressure of a mixture of gases is equal to the sum of the partial pressures of those gases.

This is the definition of Dalton's Law which is more fundamental and a better answer than statement B.

Hence the answer to this question will be option D.

Topic: Gaseous State, Physical Chemistry, A Level Chemistry, Singapore

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