Question

Avogadro’s hypothesis relates volume of gases and:

• A. mass
• B. temperature
• C. pressure
• D. number of molecules

Hint:

Avogadro’s law links the volume of a gas with the number of molecules, provided the temperature and pressure are constant.

Answer 1

The Correct Option is D

Avogadro’s Hypothesis 

Avogadro’s hypothesis states that at the same temperature and pressure, equal volumes of gases contain the same number of molecules. This hypothesis was introduced by Amedeo Avogadro in 1811 and is a fundamental principle in the field of chemistry, specifically in the study of gases.

Detailed Explanation:

Avogadro's hypothesis helps explain the relationship between the volume of gas and the number of gas molecules. It implies that the number of molecules in a gas is directly proportional to the volume, assuming the temperature and pressure are constant.

This means that if two different gases are at the same temperature and pressure, and they occupy the same volume, they must contain the same number of molecules, regardless of the type of gas. For example, if you have 1 liter of oxygen gas and 1 liter of nitrogen gas, under identical conditions of temperature and pressure, both will contain the same number of molecules, even though the gases are different.

Mathematical Representation:

The relationship can be expressed using the equation:

V ∝ n (where V is volume and n is the number of molecules or moles)

This relationship became the foundation for the definition of the mole concept and helped in the determination of Avogadro's number, which is approximately 6.022 x 10²³ molecules per mole.

Importance:

Avogadro’s hypothesis played a crucial role in advancing our understanding of the ideal gas law, molecular theory, and stoichiometry in chemical reactions. It also helped establish the concept of molar volume, which is the volume occupied by one mole of a gas at standard conditions (0°C and 1 atm pressure).

Answer 2

Avogadro's hypothesis is best pinned down by its actual statement, that at fixed temperature and pressure, equal volumes of any gas hold equal numbers of molecules, which can be written as volume is proportional to the number of molecules. Checking each option against this statement settles the question.

1. Mass: The hypothesis says nothing about the mass of gas present. Two different gases occupying the same volume under the same conditions can have very different masses, since mass depends on which gas it is, not just how many molecules are present.
2. Temperature: Temperature is one of the two conditions the hypothesis is stated at a fixed value of, it is held constant while comparing volumes, not the variable being linked to volume.
3. Pressure: Like temperature, pressure is the other condition held fixed in the statement of the hypothesis. It is a background condition for the comparison, not the quantity volume is being related to.
4. Number of molecules: The hypothesis directly states that volume is proportional to the number of molecules when temperature and pressure are both held constant. This is exactly the relationship the hypothesis describes.

Since temperature and pressure are the fixed background conditions in the hypothesis, and mass is not part of its statement at all, only the number of molecules is the quantity volume is actually related to.

So the correct answer is Number of molecules.