Victor Meyers Method
The Victor Meyer Method is a chemical procedure used to determine the boiling point of a liquid. It is based on the measurement of the pressure of an equilibrium vapor of the liquid at a given temperature.
The Victor Meyer Method is used to measure the vapour density of volatile organic compounds. This is done by vaporizing a known mass of the compound in a Victor Meyer tube and collecting the vapours into a graduated tube, displacing an equal volume of air. The volume of the vapours is then measured and converted to Standard Temperature and Pressure (STP).
Let the volume of vapours at STP be V mL
22400 mL of vapours are obtained from 1 mole of the compound.
(V/ 22400) mL of the compound will yield V mL of vapours.
Mole = $\frac{W}{Mw}$
Therefore,
W/Mw = V/22400
The molecular weight of the compound can be determined from this.
Also Read
Purification of Organic Compounds
Qualitative Analysis of Organic Compounds
Determination of Empirical and Molecular Formulas
| Element | Percentage |
|---|---|
| Carbon | 48% |
| Hydrogen | 8% |
| Nitrogen | 28% |
| Oxygen | 16% |
| Element | Percentage | Atomic Mass | Relative Number of Atoms | Simplest Atomic Ratio | Simplest Whole Number Atomic Ratio |
| Carbon | 48.0 | 12 | | | |
| Hydrogen | 8.0 | 1 | | | |
| Nitrogen | 28.0 | 14 | | | |
| Oxygen | 16.0 | 16 | | | |
Divide the percentage of atoms by the atomic mass of the element to calculate the relative number.
| Element | Percentage | Atomic Mass | Relative Number of Atoms | Simplest Atomic Ratio | Simplest Whole Number Atomic Ratio |
|---|
| Carbon | 48.0 | 12 | 48/12=4 | | |
| Hydrogen | 8.0 | 1 | 8/1=8 | | |
| Hydrogen | 8.0 | 1 | 8÷1=8 | | |
| Nitrogen | 28.0 | 14 | 2 | | |
| Oxygen | 16.0 | 16 | 16/16 = 1 | | |
The simplest atomic ratio among 4, 8, 2, and 1 is 1, which is obtained by dividing the relative number of atoms and taking the lowest number.
| Element | Percentage | Atomic Mass | Relative Number of Atoms | Simplest Atomic Ratio | Simplest Whole Number Atomic Ratio |
| Carbon | 48.0 | 12 | 48/12=4 | 4/1=4 | |
| Hydrogen | 8.0 | 1 | 8/1 | 8 | |
| Nitrogen | 28.0 | 14 | 28/14=2 | 2/1=2 | 2 |
| Element | Atomic Weight | Atomic Number | Weight/Number = Atomic Mass | Mass/Mass = Relative Atomic Mass |
|---|---|---|---|---|
| Oxygen | 16.0 | 16 | 16/16=1 | 1/1=1 |
Multiply each whole number with an integer to make it a simplest whole number; in this particular case, since all the numbers are already whole numbers, no further multiplication is necessary.
| Element | Percentage | Atomic Mass | Relative Number of Atoms | Simplest Atomic Ratio | Simplest Whole Number Atomic Ratio |
| Carbon | 48.0 | 12 | 48/12 = 4 | 4/1 = 4 | 4 |
| Hydrogen | 8.0 | 1 | 8/1 | 8 | 8 |
| Nitrogen | 28.0 | 14 | 28/14 = 2 | 2/1 = 2 | 2 |
| Element | Atomic Weight | Atomic Number | Ratio | Simplified Ratio | Simplified Fraction |
|---|---|---|---|---|---|
| Oxygen | 16.0 | 16 | 16/16 = 1 | 1/1 = 1 | 1 |
Therefore, the empirical formula of the compound is C_4H_8N_2O.
To determine the molecular formula, we need to know the molecular mass of the compound.
We need to find the empirical mass if the molecular mass of the substance is given as 200 amu.
Empirical mass = 4*12 + 8*1 + 2*14 + 1*16
100 amu
We need to determine the ratio of molecular mass to empirical mass, so we divide them.
n = (Molecular Mass)/(Empirical Mass)
n = 2
n = 2
Now, we found that molecular mass is twice the atomic mass, so the molecular formula should be equal to the empirical formula multiplied by 2.
Molecular formula: C4H8N2O x 2 = C8H16N4O2
