Hydrogen from copper sulfate

Hydrogen is produced from common materials.

Scientific name: Hydrogen is produced in a series of displacement and hydrolysis reactions.

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Safety

Wear eye protection goggles and gloves. Be careful with obtained hydrogen. It is highly flammable.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

CuSO4 + 2NaCl → CuCl2 + Na2SO4

CuCl2 + H2O → CuOHCl + HCl

3CuCl2 + 2Al → 2AlCl3 + 3Cu

2Al + 6HCl → 2AlCl3 + 3H2

Step-by-step instruction

  1. Prepare copper sulfate and sodium chloride solutions and a few pieces of aluminum foil.
  2. Pour the solution of copper sulfate into a flask with a narrow neck.
  3. Add the solution of sodium chloride into the flask.
  4. The blue solution of copper sulfate turns green
  5. Roll the foil into strips and place it into the flask.
  6. The evolution of gas begins. You can put a balloon to the neck and collect it. This gas can be used as a fuel for a hydrogen car.
  7. You can also change this experimental procedure to obtain dancing flames in the flask. The solution should occupy only about one fourth of the flask. Some small amount of diluted hydrochloric acid should be added to the obtained copper chloride solution. Use the balls of aluminum foil instead of strips. When evolution of gas begins ignite it with a lit splint. The green flame will sink back into the flask and dance.

Scientific background

This experiment demonstrates a way to obtain hydrogen from common materials. When copper sulfate is mixed with sodium chloride the exchange reaction took place. Copper (II) chloride and sodium sulfate are formed. Copper (II) chloride undergoes the hydrolysis reaction. Hydrolysis of salts is an ion exchange reaction of salt and water. Water breaks down the bonds in the salt producing new types of compounds depending on the nature of the initial substance. In the case of salt formed from a strong acid and weak base such as copper (II) chloride the bonds in a salt will break apart and the whole solution turns acidic. In our case some small amount of hydrochloric acid is produced. The driving force of the hydrolysis process is the interaction of ions with water resulting in the formation of a weak electrolyte.

As a rule aluminum foil is not a very reactive material. Aluminum in such a state does not replace metals from their salts even if it stands much higher in the reactivity series. The reason of such behavior is the presence of an oxide layer on aluminum surface. It protects the metal from reacting with other chemicals. If you place some aluminum foil to the copper sulfate solution nothing will happen. The Reaction does not proceed. But if you take copper chloride solution instead of copper sulfate the reaction starts immediately. The reason of this is the formation of complex ions between aluminum and chlorine ions which serve as very good ligands helping to destroy the oxide layer. Since aluminum becomes unprotected it readily reacts with hydrochloric acid and copper (II) chloride. In both reactions aluminum is more reactive and displaces hydrogen and copper from their compounds. Aluminum chloride, copper and hydrogen are formed.

Danger:
Coolness:
Difficulty:

Published on 09 September 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst