Chemists
do experiments under distinct conditions.
Often, a certain set of conditions gets used quite often, so chemists have
created a shortcut method of indicating those conditions. Be familiar with STP and SATP, as they will pop up in gas law questions.
Standard
Temperature & Pressure (STP):
standard
temperature = 0°C or 273.15 K
standard
pressure = 101.325 kPa
Standard
Ambient Temperature & Pressure (SATP):
standard
ambient temperature = 25.00°C or 298.15 K
standard
ambient pressure = 100.0 kPa
Combined Gas Law
Recall
that V ∝ 1/P, V ∝
T
So V ∝ T/P or PV ∝
T
For
the gas at initial conditions, P1V1/T1 = k
For
the gas at final conditions, P2V2/T2 = k
P1V1/T1
= P2V2/T2
ex.
What pressure is required to put 212 L of chlorine gas, originally at STP, into
a 52 L tank at 12.4°C?
P1
= 101.325 kPa
P1V1/T1 = P2V2/T2
V1
= 212 L 101.325 kPa(212 L)/273.15 K = P2(52
L)/285.5 K
T1
= 0 + 273.15 K = 273.15 K
P2 = 431.1 kPa
P2
= ? ∴ the
pressure is 430 kPa.
V2
= 52 L
T2
= 12.4 + 273.15 = 285.5 K
Dalton’s Law of Partial Pressures
The
total pressure of a mixture of non-reacting gases is equal to the sum of the
partial pressures of the individual gases.
Ptotal = p1 + p2
+ p3 + ---
ex.
A flask contains an air mixture that has oxygen at a partial pressure of 28 kPa
and nitrogen at a partial pressure of 110 kPa.
What is the total pressure in the tank?
p1
= 28 kPa P = p1 +
p2
p2
= 110 kPa = 28 kPa + 110 kPa
P = ? = 138 kPa
∴ the total pressure 138 kPa.
Homework:
Practice p. 542 # 1-3, 8
Learning Check p. 557 # 9-12
Student Questions:
1. Can you do p. 557 # 9, 10 & 12?
Sure can:
1. Can you do p. 557 # 9, 10 & 12?
Sure can:
3. Seriously, miss, just do them all...
