JEE Main 2020 · 7 January · morning · Single correct · +4 / −1
Amongst the following statements, that which was not proposed by Dalton was :
- (a) Matter consists of indivisible atoms all the atoms of a given element have.
- (b) Chemical reactions involve reorganization of atoms. These are neither created not destroyed in a chemical reaction.
- (c) When gases combine or reproduced in a chemical reactionn they do so in a simple ratio by volume provided all gases are the same T & P.
- (d) Identical properties including identical mass. Atoms of differemt element differ in mass.
Answer and solution
Answer (c) When gases combine or reproduced in a chemical reactionn they do so in a…
Solution
Chemistry ma’am · 3 steps
Ask who said it, not whether it is true: the gas-volume rule belongs to Gay-Lussac, not Dalton.
- What Dalton proposed. Dalton's atomic theory (1808) was about atoms: what they are, how elements differ, and what happens to atoms in a reaction. It said nothing about volumes of gases.
Statement Idea Proposed by (a) Matter is made of indivisible atoms Dalton (b) Atoms are rearranged in reactions, never created or destroyed Dalton (c) Gases react in simple whole-number ratios by volume at the same T and P Gay-Lussac (law of gaseous volumes) (d) Atoms of one element have identical mass; different elements differ in mass Dalton - The odd one out. Gay-Lussac stated the law of gaseous volumes in 1808 from experiments on reacting gases. Dalton's theory could not even explain it. Avogadro's hypothesis was needed for that.
- So. Statements (a), (b) and (d) are all Dalton's postulates. Only (c) was not proposed by Dalton, so the answer is (c).
The idea to keep. Dalton's postulates are all about atoms: indivisible, identical within an element, rearranged in reactions. Any rule about gas volumes is Gay-Lussac's.
Answer from the NTA final answer key. Solution by PrepWiser.