To determine which proportionality applies to Avogadro's Law, let's first recall the essence of Avogadro's Law in chemistry.
Avogadro's Law states that the volume of a gas (V) is directly proportional to the number of moles of the gas (n) when the temperature and pressure are held constant. The key idea here is the relationship between volume (V) and the number of moles (n).
Given the four options:
1. [tex]\( V \propto \frac{1}{p} \)[/tex] - This suggests that the volume is inversely proportional to the pressure, which is related to Boyle's Law, not Avogadro's Law.
2. [tex]\( V \propto T \)[/tex] - This suggests that the volume is directly proportional to the temperature, which is related to Charles's Law, not Avogadro's Law.
3. [tex]\( P \propto T \)[/tex] - This suggests that the pressure is directly proportional to the temperature, which is related to Gay-Lussac's Law, not Avogadro's Law.
4. [tex]\( V \propto n \)[/tex] - This suggests that the volume is directly proportional to the number of moles, which is precisely what Avogadro's Law states.
Thus, the correct proportionality that applies to Avogadro's Law is:
[tex]\[ V \propto n \][/tex]
So the correct answer is:
[tex]\[ 4 \][/tex]
This shows that as the number of moles of gas increases, the volume of the gas also increases, provided the temperature and pressure remain constant.