Animated Solution for Chemistry - Basic Concepts in Chemistry: Among the following statements, that which was not proposed by Dalton was

Dalton vs. Gay-Lussac

When we dive into the history of chemistry, John Dalton stands as a monumental figure. His atomic theory, proposed in the early 19th century, was a massive leap forward. It provided a microscopic explanation for the macroscopic laws that chemists had been observing, such as the Law of Conservation of Mass and the Law of Definite Proportions.

Dalton's vision of the universe was beautifully simple and mechanical. He proposed a few core ideas that shaped chemistry for decades:

1. Indivisible Atoms: He believed that all matter is composed of tiny, indestructible particles called atoms. Imagine them as solid, microscopic billiard balls. 2. Identical Properties: He stated that all atoms of a specific element are exactly identical in mass and properties. An atom of oxygen is identical to every other atom of oxygen, but different from an atom of carbon. 3. Reorganization in Reactions: According to Dalton, chemical reactions are merely the reshuffling or reorganization of these atoms. Atoms are neither created nor destroyed; they just change their partners.

These postulates perfectly explain why mass is conserved in a reaction. If you are just rearranging indestructible blocks, the total weight of the blocks cannot change!

While Dalton was theorizing about invisible atoms and their masses, another brilliant scientist, Joseph Louis Gay-Lussac, was busy in his laboratory experimenting with gases. Gay-Lussac wasn't measuring mass; he was measuring volume.

Gay-Lussac made a fascinating empirical observation: when gases react together to form products, they do so in a simple ratio by volume, provided the temperature and pressure remain constant. For example, $1$ volume of hydrogen reacts with $1$ volume of chlorine to produce $2$ volumes of hydrogen chloride gas. The ratio is a simple $1:1:2$.

Interestingly, Dalton initially struggled to accept Gay-Lussac's findings. Dalton's model assumed that atoms of different elements had different sizes, and he couldn't reconcile how different sized atoms could result in such perfectly simple volume ratios.

It wasn't until Amedeo Avogadro came along and proposed that equal volumes of gases contain equal numbers of molecules (not just single atoms) that the bridge between Dalton's atomic masses and Gay-Lussac's gas volumes was finally built.

Therefore, when we look at the options provided in the question, the statement about gases combining in simple volume ratios is the clear outlier. It is the defining statement of Gay-Lussac's Law, not Dalton's Atomic Theory.