Question

Compare Boyle's law, Charles's law, and Avogadro's law. a. What remains constant in each law? b. What are the variables in each law? c. What do the graphs for these laws look like? d. Write each law with V isolated. Using these equations and the graphs from part c, which law(s) show a directly proportional relationship? How can you tell?

Answer 1

Answer:

a)

In Boyle's Law, the variable that remains constant is the absolute temperature of the gas.

In Charle's Law, the variable that remains constant is the pressure of the gas.

In Avogadro's Law, the variables that remain constant are pressure and temperature of the gas.

b)

In Boyle's Law, the variables involved are pressure and volume: the law states that for a fixed mass of ideal gas at constant temperature, the pressure of the gas is inversely proportional to the volume:

$p\propto \frac{1}{V}$

where p is the pressure of the gas and V the volume.

In Charle's Law, the variables involved are volume and temperature: the law states that for a  fixed mass of ideal gas at constant pressure, the volume of the gas is directly proportional to the temperature:

$V\propto T$

where V is the volume of the gas and T the temperature.

In Avogadro's Law, the variables involved are the volume and the number of moles: the law states that for an ideal gas kept at constant pressure and temperature, the volume of the gas is directly proportional to the number of moles:

$V\propto n$

Where V is the volume of the gas and n the number of moles.

c)

See the graphs of the three Laws in attachment:

- First graph: Boyle's Law, which shows that the pressure of the gas is inversely proportional to the volume

- Second Graph: Charle's Law, which shows that the volume of the gas is directly proportional to the absolute temperature

- Third graph: Avogadro's Law, which shows that the volume of the gas is directly proportional to the number of moles of the gas

d)

Here we want to re-write the three laws by making V the subject.

For Boyle's law, we get:

$V\propto \frac{1}{p}$

For Charle's Law, we get:

$V\propto T$

For Avogadro's Law, we get:

$V\propto n$

Therefore, we see that the two laws that show a direct proportionality are Charle's Law and Avogadro's Law, while Boyle's Law shows an inverse proportionality between the two variables.