1
Determination of molecular molecular mass mass of volatile liquid.
Ha
.
NAME: Muhammad Habibu Abdullahi Contact Numbers: +256780983362, +2348032721286.
[email protected],, E-mail addresses:
[email protected] [email protected]/gmail.com. FACULTY: Sciences Department: Chemistry Department PAPER: Physical Chemistry
In Details, the Victor Meyer`s method for determination of molecular mass of volatile liquids.
…Not Strength, but Continuous effort is the key to unlocking our Potentials! A.M Habibu
Ha
.
2
Determination of molecular molecular mass mass of volatile liquid.
The Victor Meyer`s Method to determine the Molecular Mass of Volatile Liquid. The Victor Meyers apparatus is the standard laboratory method for determining the molecular weight of a volatile liquid. It was developed by Victor Meyer, who spelled his name Victor in in publications at the time of its development. Experiment: To Experiment: To determine the molecular mass of a volatile liquid. Apparatus Involved: Involved: Victor Meyer`s tube, Outer Copper Jacket, Hoffmann`s Bottle, Graduated Glass Tube. 2
Victor Meyer`s tube : This is a hard glass tube of 1 cm cross-sectional area of 75 cm in length. The tube has a bulb at its lower end and an exit tube at the upper end of the tube.
Outer Copper Jacket : The outer copper jacket has a round bulb at its lower end. The victory Meyer's tube is suspended into this jacket with the help of a hard rubber cork.
Hoffmann`s Bottle: This is a small (3 mm diameter, 35 mm length) glass bottle with a very light light stopper. This This is used for introducing the sample into the Victor Meyer's tube.
Graduated Glass Tube: This is a burette-like glass tube graduated in millilitres. This is used for f or collecting the displaced air.
Please move to the next page.
A.M Habibu
3
Determination of molecular molecular mass mass of volatile liquid.
The Procedure: A known mass of a volatile solid or liquid under examination is converted into its vapour form by heating in a Victor Meyer's tube. The vapour displaces its own volume of air. The volume of air displaced at experimental temperature and pressure is calculated. Then volume of air displaced at Standard Temperature and Pressure
−2 3 (STP) is calculated. Using this, mass of air displaced at 2.24x10 m of vapour at STP is calculated. This value represents the molecular mass of the substance. The apparatus consists of an inner Victor Meyer's tube, lower end of which is in form of a bulb. The upper end of tube has a side tube that leads to a trough filled with water. The Victor Meyer's tube is surrounded by an outer jacket. In the outer jacket, a liquid is placed, which boils at a temperature at least 30K than the substance under examination. A small quantity of glass-wool or asbestos pad covers the lower end of the Victor Meyer's tube to prevent breakage, when a glass bottle containing the substance under examination is dropped in it. The liquid in the outer jacket is heated until no more air escapes from the side tube. Then, a graduated tube filled with water is inverted over the side tube dipping in a trough filled with water. A small quantity of substance is weighed exactly in a small stoppered bottle and is dropped in the Victor Meyer's tube and sealed immediately. immediately. The bottle falls on the pad and its contents suddenly suddenly change into vapour, blows out the stopper and displaces an equal volume of air in graduated tube. The volume of air displaced is measured by taking the graduated tube out, closing its mouth with thumb and dipping in a jar filled with water. When water levels inside and outside the tube is equal, the volume of air displaced is noted. The atmospheric pressure and the laboratory temperatures are noted.
A.M Habibu
4
Determination of molecular molecular mass mass of volatile liquid.
Calculations: Let, The mass of the organic compound taken be = W g Volume of air displaced = V 1 mL Atmospheric pressure = P mm of Hg o
Room temperature, T1 = t C = (t + 273)K o
Aqueous tension at t C = p mm of Hg Pressure of the dry air, P 1 = (P-p) mm Hg
The volume of the displaced air is equal to the volume of vapours formed from the given mass of the compound. So, by using the mole concept, one can write,
V mL of vapour weigh = W g
Therefore,
Please move to the next page.
A.M Habibu
5
Determination of molecular molecular mass mass of volatile liquid.
Example. A volatile organic compound weighing 0.2 g, on heating in Victor Meyer's tube, o
displaced 30 mL of air at 27 C and 756 mm atmospheric pressure. Determine the molecular mass of the compound (Aqueous tension at 27C = 26 mm).
Solution. Mass of the substance taken = 0.2 g Volume of air displaced = 30 mL o
Temperature = 27 C = (27 + 273) K = 300 K Atmospheric pressure = (756 - 26) mm Hg = 730 mm Hg Then,
Therefore, Volume of the vapours at NTP = 22.5 mL Then,
Hence, the molecular mass of the compound is = 199.1g
A.M Habibu
6
Determination of molecular molecular mass mass of volatile liquid.
Please Note that: that: 1. One mole of any volatile substance when vaporized gives vapour that occupy 22.4 L of volume under NTP conditions. 2. (STP) means Standard Temperature and Pressure
References. 1. Intermediate Chemistry, Inorganic and Physical. Prescott (1965). 2. General Chemistry-John Russell by McGraw Hill International Editions 3rd edition 3. University General Chemistry-An Introduction to Chemical Science edited by CNR Rao by McMillan Indian Ltd. 4. Search Websites i.e. Google and Wikipedia.
Ha
A.M Habibu
.
