# Chapter 13 section 2

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Chapter 13
section 2
Gas conditions that don’t
change
Molar volume of a gas (Avogadro’s
principle)
 22.4 L of any gas = 1 mol at Standard
Temperature and Pressure (STP)
 STP = 1 atm and 0 degrees Celsius
 Convert the following volumes of a gas at
STP to moles by using
 22.4 L/mol as the conversion factor.
 2.00 L
 2.00L x 1 mol/22.4 L = 0.0893 mol
 7.34 L
 =0.328 mol
 To use 22.4L you must be at STP. Moles
may need to be converted to grams by x
by the molar mass or mass to mol by
dividing
 Do 20-25 page 453 check odd problems
on page 999
 20) 1.03 L 22) 103 mL 24) 3600L
 What quantity of gas, in moles, is
contained in 2.21 L at STP?
 a)0.0454 mol            c).1974 mol
b).0987 mol             d).2948 mol
b
Ideal gas law PV=nRT
 Use atmospheres or kPa for Pressure
 Liters for Volume
 Moles for n
 Kelvins for Temperature
 R is a constant that is .0821 if P is atm,
8.314 if P is kPa
   Gas law animation
 Calculate the number of moles of a gas
contained in a 3.0-L vessel at 102 K with a
pressure of 1.50 atm.
 Are there any changing values?
 No, then use PV = nRT R = 0.0821 if atm
 (1.5 atm)(3.0 L) = n (0.0821)(102K)
 0.54 mol
 Calculate the number of grams of H2 gas
contained in a 2.00-L container at -100.0
oC with a pressure of 120 kPa.

 PV = nRT
(120 kPa)(2.0L) = n (8.314)(173 K)
 n = 0.167 mol
 g = 0.167 mol x 2g/mol = 0.334 g
 Do problems 26-29 page 455
 Answers to odd problems on page 999
 26) -266 oC 28) 5.14 atm
 What volume does .0685 mol of gas
occupy at STP?
 a).3707 mol             c)1.53 L
b).7515 mol             d)3.06 L
c
Real gases vs. Ideal gases
Real gases vs. Ideal gases
 Real gases deviate some at high
pressures and low temperatures
 Why?
 They take up space and forces of
attraction come into play