how could you show experimentally that the molecular formula of propene is C3H6, not CH2?
Do an ebuilloscopic ( boiling point elevation) or cryoscopic (freezaing point depression) experiment.
To experimentally demonstrate that the molecular formula of propene is C3H6 and not CH2, you would need to perform a combustion analysis or other chemical tests. Here's how you can approach this experimentally:
1. Combustion Analysis: One method to determine the molecular formula of a compound is through combustion analysis. In this experiment, the compound is burned in the presence of excess oxygen to determine the amounts of carbon dioxide (CO2) and water (H2O) produced.
- Take a known amount of propene in a combustion chamber.
- Supply excess oxygen and initiate combustion.
- Capture the resulting gases (CO2 and H2O) and measure their quantities precisely.
- Using stoichiometry, calculate the ratio of carbon atoms in CO2 to hydrogen atoms in H2O.
If propene were CH2, the stoichiometry of the reaction would yield one CO2 molecule and one H2O molecule. However, if it is C3H6, the stoichiometry would yield three CO2 molecules and three H2O molecules.
2. Molecular Mass Determination: Another experimental approach is to determine the molecular mass of propene using mass spectrometry or other methods.
- Obtain a pure sample of propene.
- Analyze the sample using techniques such as mass spectrometry.
- Measure the molecular mass of the compound.
If propene were CH2, the molecular mass would be significantly lower than if it were C3H6.
By performing these experiments and comparing the results with the expected stoichiometric values for propene, you can conclusively demonstrate that the molecular formula of propene is C3H6 and not CH2. Remember that multiple experiments and techniques might be needed to obtain accurate and reliable results.