Page 22 - A Working Method Approach For Introductory Physical Chemistry Calculations

6 Chapter I
Solution:
The gas is at constant pressure, and therefore Charles’s Law can be
applied:
Hence initially, Vl = kT1 or k = Vl/Tl
Hence k = (200 m3)/(288 K)
= 0.694 cm3 K-’
NOW V2 = kT2, SO, V2 = (0.694 cm3 K-’) x (303 K)
= 210.42cm3

Answer: Final Pressure = 210.42 C&

Avogadro’s Law
This states that equal volumes of gases, measured at the same
temperature and pressure, contain equal numbers of molecules.

i.e. Avogadro’s Law: V a n, where n = the amount of gas (measured
in
r moles).
The mole is defined as the amount of a substance which contains as
many elementary species as there are atoms in 12 g of the carbon-12
isotope. A mole contains 6.02205 x particles, where NA is defined
as Avogadro’s constant i.e. NA = 6.02265 x mol-’.

Ideal Gases
An ideal gas is a theoretical concept, a gas which obeys the gas laws
perfectly. If the three gas laws are combined, the resulting equation is
the equation of state of an ideal gas:
(a) Boyle’s Law : V oc 1 /p
(b) Charles’s Law : V oc T
(c) Avogadro’s Law : V a n
(a), (b) and (4 =$ Va (TUP
+pVanT
+ pV = knT,

where k is another constant of proportionality called the Universal
Gas Constant, R.
[Zdeal Gas Equation: pV = nRT I