Who proposed the law of reciprocal proportions?

Correct answer: Richter

The direct answer is A: Richter. The law of reciprocal proportions is associated with Jeremias Benjamin Richter. To understand the idea, imagine three elements, X, Y and Z. If a fixed mass of X combines separately with fixed masses of Y and Z, then the masses of Y and Z are related in a simple whole-number ratio to the masses in which Y and Z combine with each other. It is a law about quantitative mass relationships in chemical combinations. Option A is correct because Richter proposed this law. Option B, Proust, is associated with the law of definite proportions, which says that a pure compound always contains its elements in a fixed mass ratio. Option C, Gay-Lussac, is associated with combining volumes of gases, especially when gases react in simple volume ratios. Option D, Boyle, is associated mainly with the pressure-volume relationship of gases, expressed as Boyle's law. These scientists may all appear in chemistry questions, so attach each name to its distinctive law. Memory cue: Richter = reciprocal proportions; Proust = definite proportions; Gay-Lussac = gas volumes; Boyle = pressure and volume.