The first test to try and identify what we had collected in the test tube, was a test for hydrogen. This was a simple test and simply involved putting a lighted splint into the test tube. If a ‘pop’ occurred then hydrogen was present and the splint would be extinguished. If no hydrogen was present, nothing happens. The outcome of this test was as follows:
As you can see we collected 8 test tubes of the gas given off and five of them turned out to be positive in the hydrogen test therefore we can safely say that hydrogen was a gas present in the gases we collected.
The next test was to investigate if there was an alkene present, and since cracking produces an alkene if the test is positive then it reflects a successful ‘crack’. The process to discover if an alkene is present is once again quite simple. We added three or four drops of bromine solution to the gas, replaced the stopper on the test tube and shook it for about 10 seconds. If the solution went see-through or clear then an alkene was present. If the solution stayed a shade of orangey yellow then no alkene was present and therefore the test was unsuccessful. The results were as follows:
As you can see from our results, again, five out of eight test tubes proved positive and therefore resulting in the discovery of an alkene and a successful test.
Conclusion
After having carried out the test, and looking back on our results, we can now say that the test was successful and therefore conclude that in the gasses collected, hydrogen and an alkene were present. We conclude that the most likely gas collected from the test tube was ethene as this is an alkane and contains hydrogen, also ethene is a very useful hydrocarbon and in high demand. Many large hydrocarbons are cracked to extract this product which has many uses, such as:
- Production of poly(e)thene
- Production of industrial alcohol
- Production of styrene and therefore polystyrene
- Production of chloroethane. Chloroethane is used to manufacture tetraethyl lead. Tetraethyl lead is the lead additive in leaded petrol
