Standard Temperature and Pressure STP

1
Standard Temperature and Pressure (STP)
STP is defined as 1.00 atm and 0.00 oC.
Temperature (T) a measure of the average
kinetic energy of the
particles in an
object. (All gas calculations must be in
the unit Kelvin
(K).) K oC 273
2
Pressure (P) the force per unit area on a
surface.

• Standard P
• 760. mm
• 760. torr
• 1.00 atm
• 14.7 psi
• 101.3 kPa

3
Barometer and Manometer
4
Daltons Law of Partial Pressure

• The total pressure of a mixture of gases is
• equal to the sum of the partial pressures of
• each gas in the mixture. (PT depends on
• the total number of particles (Moles)).
• PT P1 P2 P3

5
If the total pressure of a container is equal to
8.4 atm and there are 1.25 moles of He and 0.50
moles of H2 in the container, what is the partial
pressure of each gas?

• PHydrogen (8.4 atm) x 0.50 moles
• 1.75 moles
• PHydrogen 2.4 atm
• PHelium (8.4 atm) x 1.25 moles
• 1.75 moles
• PHelium 6.0 atm

6
Gases Collected by Water Displacement

• Because it is being collected over water you
• must subtract out the partial pressure due to
• water vapor that was collected along with
• the other gases.
• PT Pgas Pwater vapor
• Pgas PT Pwater vapor

7
Boyles Law (temperature is held constant)

• P a 1
• V
• VP k
• For a system
• V1P1 V2P2

8
If I have 5.6 liters of gas in a piston at a
pressure of 1.5 atm and compress the gas until
its volume is 4.8 L, what will be the new
pressure inside the piston?

• P1V1 P2V2
• P2 P1V1
• V2
• P2 (1.5 atm)(5.6 L) (4.8 L)
• P2 1.8 atm

9
Charles Law (pressure is held constant)

• V a T
• V k
• T
• for a system
• V1 V2
  T1 T2

10
If I have 45 liters of helium in a balloon at 25
oC and increase the temperature of the balloon to
55 oC, what will be the new volume of the balloon?

• V1 V2
  T1 T2
• V2 V1 T2
• T1
• V2 (45 L)(328 K)
• (298 K)
• V2 50. L

11
Gay-Lussacs Law (volume is held constant)

• P a T
• P k
• T
• For a system
• P1 P2
• T1 T2

12
At 120.0 oC the pressure of a sample of nitrogen
is 1.7 atm. What will the pressure be at 205 oC,
assuming constant volume?

• P1 P2
• T1 T2
• P2 P1 T2
• T1
• P2 (1.7 atm)(478 K)
• (393 K)
• P2 2.1 atm

13
Avogadros law (temperature and pressure are
held constant)

• V a n
• V k
• n
• V1 V2
• n1 n2

14
Calculate the number of liters occupied by 3.00
moles of oxygen at STP.

• The volume of 1 mole any gas at STP
• occupies a volume of 22.4 L.
• 3.00 moles O2 22.4 L O2 67.2 L of O2
• 1 mole O2

15
Combined Gas Law(mole of the gas are held
constant)

• Two sets of conditions an initial set of
• conditions and a final set of conditions
• P1V1 P2V2
  T1 T2

16
A toy balloon has an internal pressure of 1.05
atm and a volume of 5.00 L. If the temperature
where the balloon is released is 20. oC, what
will happen to the volume when the balloon rises
to an altitude where the pressure is 494 torr and
the temperature is 15. oC?

• V2 P1V1T2
• P2T1
• V2 (1.05 atm)(5.00 L)(258 K)
• (293 K)(0.650 atm)
• V2 7.11 L

17
Ideal Gas Law

• PV nRT
• Ideal gas Constant (R) 0.0821 L ? atm
• mole ? K

18
If 246.4 g of oxygen gas is in a container at a
pressure of 0.0900 atm and a temperature of 56
oC, what is thevolume of the container that the
oxygen is in?

• PV nRT
• V nRT
• P
• V (7.700 mole)(0.0821 L ? atm)(329 K)
• (mole ? K)(0.0900 atm)
• V 2310 L

19
Gas Laws Stoichiometry

• Hydrogen gas and zinc sulfate are produced
• when zinc reacts with sulfuric acid. If 124 mL
• of wet H2 gas is collected over water at 24oC
• and a barometric pressure of 725 mm Hg,
• how many grams of Zn have been
• consumed? (the vapor pressure of water at
• 24 oC is 22.38 mm Hg).

20

• Zn H2SO4 ? H2 ZnSO4
• 725 mm 22.38 mm 702.62 mm 703 mm 0.925
  atm
• nH2 PV (0.925 atm) (0.124 L) (mole ? K)
  RT (0.0821 L ? atm) (297 K)
• 0.00470 moles H2
• 0.00470 moles H2 1 mole Zn 65.39 g Zn
  0.307 g Zn
• 1 mole H2 1 mole Zn