Exploding Hydrogen
A clean fuel for the future?
The picture above shows an airship called the Hindenburg. Hydrogen was used to fill airships because of a property demonstrated in this video clip. Unfortunately in 1937 it burst into flame as it was landing after a transatlantic flight in New Jersey, USA. Of the 92 passengers and crew, 36 were killed. The disaster effectively ended the use of airships for passenger transport, even though another gas, helium, could be used instead. Helium has the advantage of being extremely unreactive.
Aim
The aim of this experiment was to make and burn hydrogen gas.
Method
In order to make the hydrogen gas we added a large strip of magnesium metal into a conical flask containing 100ml of Hydrochloric acid. Safety goggles are worn to protect our eyes and the flask is kept away from the body.
The metal reacted vigorously, fizzing on the surface of the acid as it dissolved, producing the gas. The gas was collected in a plastic bag held over the top of the conical flask.
The bag was held open for a moment to allow some air to enter the bag as we would need to have oxygen present for the hydrogen to burn and then tied it in a knot. The bag was then placed in a boss clamp behind a safety screen. We fixed a wooden splint to the end of a 1 metre rule and then used this to set the bag alight.
Results
The bag exploded with a loud bang and on one occasion the safety screen was dented.
Conclusion
When a metal is added to an acid the chemical reaction that takes place is an irreversible change that results in the formation of the metal salt and hydrogen. This can be written as:
Metal + acid --> metal salt + hydrogenFor our experiment we used magnesium metal and hydrochloric acid to produce our hydrogen so for our reaction we write:
Mg + 2HCl --> MgCl2 + H2The other product of our reaction is magnesium chloride. Hydrogen can only burn when oxygen is present. When the hydrogen burns it does so very quickly which is why we get an explosion. When hydrogen burns it forms water. This is an irreversible chemical reaction that can be written:
2H2 + O2 --> 2 H2OHydrogen has been proposed as a fuel for cars because when it burns it produces lots of energy and no pollution in the form of carbon dioxide or other oxides associated with combustion of fossil fuels such as sulphur dioxide and oxides of nitrogen.