Correct Option
The correct option is 2 only.
Explanation
Avogadro's Law provides a fundamental relationship between the volume of a gas and the amount of substance it contains. It was instrumental in reconciling Dalton's Atomic Theory with Gay-Lussac's Law of Combining Volumes by distinguishing between atoms and molecules.
Statement-wise Analysis
- Statement 1 is Incorrect. Avogadro’s Law states that equal volumes of all gases at the same temperature and pressure contain an equal number of molecules (or moles), not equal masses. Since different gases have different molar masses, equal volumes will have different masses.
- Statement 2 is Correct. Prior to Avogadro, it was difficult to explain why 2 volumes of hydrogen react with 1 volume of oxygen to give 2 volumes of water vapor without assuming the splitting of atoms (which violated Dalton's theory). Avogadro proposed that gases like hydrogen and oxygen exist as diatomic molecules ($H_2$ and $O_2$). This allowed the reaction to be understood as $2H_2 + O_2 \rightarrow 2H_2O$, perfectly aligning the molecular ratio with the observed volume ratio.
Key Takeaway
Key Takeaway: Avogadro's Law establishes that gas volume is directly proportional to the number of molecules ($V \propto n$) under constant temperature and pressure, implying that gas molecules can be polyatomic.