•Gas pressure is due to the force of gaseous particles colliding with their container. •Torricelli invented the barometer to measure atmospheric pressure. •Units used: mmHg, atm, kPa, psi •Using a manometer: gas pressure > air pressure P gas = P atm + h gas pressure < air pressure P gas =
18
Embed
Gas pressure is due to the force of gaseous particles colliding with their container. Torricelli invented the barometer to measure atmospheric pressure.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
•Gas pressure is due to the force of gaseous particles colliding with their container.
•Torricelli invented the barometer to measure atmospheric pressure.
•Units used: mmHg, atm, kPa, psi
•Using a manometer: gas pressure > air pressure Pgas = Patm + h gas pressure < air pressure Pgas = Patm – h
•Describe the relationship between pressure and volume of a gas.
•Describe the relationship between temperature and volume of a gas at a constant pressure.
•Define absolute zero.
•Solve problems for both Boyle’s and Charles’ Law.
Pre
ssur
e (k
Pa)
Volume (mL)
BOYLE’S LAW – Pressure vs. Volume
BOYLE’S LAW:
The volume of a given amount of gas (held at a constant temperature) varies inversely with the pressure.
P α 1 V
What will be the volume of 40 L of gas (held at a constant temperature) if the pressure is doubled? Reduced to 1/3rd ?
P α 1 V
1/3 α 1 1/3
2 α 1 2
1 = 3 1/3 120 L
20 L
PV = k
=
P1V1P2V2
P α 1 V
If 3 L of gas is initially at a pressure of 1 atm, what would be the new pressure required for a volume of 0.5 L?
6 atm of pressure will change 3 L of a gas at 1 atm to 0.5 L.
=
P1V1 P2V2
=
(1)(3) P2 (0.5)
A syringe contains 20 mL of a gas at 100 kPa. The pressure in the syringe is changed to 25 kPa. What is the new volume of the gas?
The gas will expand to 80 mL.
=
P1V1 P2V2
=
(100)(20) V2(25)
Absolute Zero
Jacques Charles (1746-1823) • Volume of gas changed with only 1oC change in temperature.
An increase of 273°C, doubled the volume.
V α T
CHARLES’S LAW: Volume of a given gas (held at a constant pressure) varies directly with the temperature
Temperature (oC)
Vol
ume
(mL
)
CHARLES’S LAW – Temp vs. Volume
William Thomson (1824-1907) • Created Kelvin Scale where –273°C is the lowest temperature possible or Absolute Zero.
“Hypothetical” – called an ideal gas model:• predicts that with zero kinetic energy comes zero volume.
TK = TC + 273 TC = TK - 273
Stated as “315 Kelvin”- no degrees.
Ideal Gas Model:• engaged in random motion (normal)• obey conservation of energy (normal)• non-interacting particles
(IMFs alter results)
Most real gases behave like “ideal gases,” butformula fails at lower temperatures OR higher pressures.