Pressure/Volume question. A2 Physics

[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.

 

[RSG_9]

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

 

[cepheid]

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?