# Pressure/Volume question. A2 Physics

• RSG_9
In summary, the pressure of air in a flask was increased using a hand pump, both with and without powder in the flask. The initial volume of air in the hand pump was calculated to be 2.7 x 10^-5 m^3. Using the ideal gas law, the ratio of pressures was found to be 1.23, but without knowing the ambient temperature, it is not possible to calculate the new amount of gas in the flask. Therefore, it is also not possible to calculate the volume and density of the powder.
RSG_9

## Homework Statement

A hand pump was used to raise the pressure of the air in a flask of volume 1.2 x 10^-4 m^3, without and then with powder in the flask.
- Without powder, pressure increased from 110kPa to 135kPa
- With 0.038kg of powder, pressure increased from 100kPa to 141kPa

1) Show that the volume of air in the hand pump initially was 2.7 x 10^-5 m^3.
2) Calculate the volume and the density of the powder.

## Homework Equations

pV=nRT

P=pressure V=volume n=#of moles R=gas constant T=temp

## The Attempt at a Solution

For the first part, I found the increase in pressure factor to be 1.23, multiplied this to the volume, then took away the original volume which got me an answer of 2.76x10^-5... I wasn't sure if that was the right method to take so I didn't want to start the second part without fully understanding the first.

I have solved this now. If anybody would like to know the solution for future reference I will be happy to help.

For the first part, since the volume of the flask is constant, when you add gas using the pump, it seems to me that both the pressure and temperature will go up. Since you know the ratio of pressures, it seems to me that the best you can do using the ideal gas law is to say that

n2T2 = 1.23 n1T1

Without knowing the ambient temperature T1, I don't see how you would solve for the new amount of gas in the flask n2. I think you need to know this, because you need to then use Avogadro's law to compute how much volume the added amount of gas (n2-n1) would have occupied at ambient temperature. Was T1 given in the problem, or am I just missing something?

## 1. What is the relationship between pressure and volume?

The relationship between pressure and volume is known as Boyle's Law. It states that at a constant temperature, the pressure of a gas is inversely proportional to its volume. This means that as pressure increases, volume decreases and vice versa.

## 2. How does temperature affect pressure and volume?

According to Charles's Law, the volume of a gas is directly proportional to its temperature, as long as pressure and amount of gas are kept constant. This means that as temperature increases, volume also increases and vice versa. However, this relationship only holds true for gases at low pressures.

## 3. What is the formula for pressure and volume?

The formula for pressure is P = F/A, where P is pressure, F is force, and A is area. The formula for volume is V = lwh, where V is volume, l is length, w is width, and h is height. These formulas can be used to calculate pressure and volume in various situations.

## 4. How does pressure and volume affect gas behavior?

Pressure and volume have a direct impact on the behavior of gases. As pressure increases, gas molecules are forced closer together, resulting in a decrease in volume. This can also cause an increase in temperature. Similarly, as volume decreases, gas molecules collide more frequently, resulting in an increase in pressure.

## 5. How do pressure and volume changes affect gas laws?

Changes in pressure and volume can affect various gas laws, such as Boyle's Law, Charles's Law, and the Ideal Gas Law. For example, if the volume of a gas is decreased while keeping pressure constant, the temperature must increase to maintain the same amount of gas molecules. This is known as Gay-Lussac's Law.

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