Molecular Weight By Dumas Method

Molecular Weight by Dumas Method

In your text (Chang, tenth Ed) : 5.4 The idealistic Gas Equation, especially the
Density and Molar commode of a Gaseous Substance subsections

Purpose: The experimental object of the molecular weight of a volatile liquid sample distribution and the parsimoniousness of its desiccation are used to illustrate the uses of the Ideal Gas Law.

Background:
The Ideal Gas Law is:PV = nRT(Eqn. 1)

where
P = pressure in atm,
V = volume in L,
T = temperature in K, and
R = 0.082056 L atm/(mol K), the Gas Constant

It describes, with intimately precision, the behavior of m any real gases over a immense range of pressures and temperatures. Even when there is deviation from ideality, it is useful as a starting point in physical analysis
Recalling that density is mass/volume, Eqn. 1 can be re-written to derive the compare for the density of a gas, assuming ideal behavior:
n = P Now multiply both sides by MW:n(MW) = P (MW)
VRT V RT

n(MW) is # moles x grams/mol = grams = mass, m thence:

m = (P)(MW) = d , density (mass/volume, in grams/ liter )(Eqn.



2)
V RT

where m = mass , in grams and MW = molecular weight, in grams/mole

Therefore, at fixed P & T, the measurement of the mass of a vapor in a known volume will put the density of the vapor under those conditions. Since the MW and R are constant for a given gas, density measured at compulsive experimental T, P conditions can be scaled to any desired T,P (usually STP, 273 K, 1 atm) by the fol miserableing ratio:

d1 T1 =d2 T2 (Eqn. 3)
P1 P2

If P and T are also measured, the molecular weight of the heart and soul can be determined by another late algebraic re-arrangement of Eqn. 2:

MW = m R T (Eqn. 4)
PV

Overview of affair:
In this experiment, a small amount of a low boiling point (If you want to get a overflowing essay, order it on our website: Orderessay



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