Which of the following best explains how relative atomic mass could be determined from the type of data available to Dalton?


A. By determining the mass of oxygen contained in a sample of water, its exact atomic mass could be determined.


B. By comparing the masses of hydrogen and oxygen contained in a sample of water, the exact atomic masses could be determined.


C. By comparing the mass of hydrogen in the two “parts” of hydrogen and the mass of oxygen in the one “part” of oxygen in water, the relative atomic masses could then be determined.


D. A and B are correct.


E. A, B, and C are all correct.

The answer is option C: By comparing the mass of hydrogen in the two “parts” of hydrogen and the mass of oxygen in the one “part” of oxygen in water, the relative atomic masses could then be determined.

To understand why option C is the best explanation, let's start by looking at the type of data available to Dalton. Dalton did not have access to the exact atomic masses of elements as we do today. However, he could determine the ratios in which elements combined to form compounds.

In the case of water (H2O), Dalton could analyze the compound and determine that it consists of two parts of hydrogen and one part of oxygen. He knew that compounds are made up of atoms in fixed ratios, so if he could determine the mass of hydrogen in the two parts and the mass of oxygen in the one part, he could compare the relative masses.

By comparing the ratios, Dalton could then assign relative atomic masses to hydrogen and oxygen. This method allowed him to determine the ratio of hydrogen to oxygen in water, which is 2:1. From this information, he was able to deduce that oxygen atoms are around 16 times heavier than hydrogen atoms, giving oxygen a relative atomic mass of approximately 16.

Option A is incorrect because Dalton did not have a method to determine the exact atomic mass of oxygen directly from a water sample.

Option B is incorrect because comparing the masses of hydrogen and oxygen in a water sample alone does not provide information about their relative atomic masses.

Option D and E are incorrect because option B is not a valid method and option A is not a method available to Dalton.