How to Separate Hydrogen From Oxygen in Water to Use in Cars

Some vehicles use hydrogen gas rather than gasoline in an internal combustion engine. As of 2010, these vehicles are generally available as demonstration models or in a leasing arrangement rather than for general public use. Water molecules are composed of hydrogen and oxygen atoms, which can be separated by passing an electrical current through the water. This process is known as electrolysis and can be used to liberate hydrogen from water.

Things You'll Need

• Water
• Sodium hydroxide
• 3 beakers
• Hoffman voltameter
• 2 test tube holders
• 2 test tubes
• 2 rubber hoses
• 9-volt battery
• 2 test tube stoppers

Instructions

1. Build a Hoffman voltameter or buy it from a laboratory supply store. This piece of equipment is an assembly of tubing in the shape of an E on its side such that the free ends of the legs are pointed up. The top end of the middle vertical tube is open and the two vertical tubes on the side are closed with gas inlets at the top. The two vertical side tubes also have electrodes on the inside of the tubes that lead outside the tubes through watertight holes.

2. Mix an electrolyte with water to form an electrolytic solution. An electrolyte may be any substance that will allow the water to conduct electricity. Sodium hydroxide is a common electrolyte for the electrolysis of water. Add one part sodium hydroxide to four parts water by weight and mix thoroughly.

3. Attach rubber tubing to the two gas inlets on the vertical side tubes to form an airtight seal. Fill the Hoffman voltameter with electrolytic solution by pouring it into the middle vertical tube.

4. Fill a test tube and beaker full of water. Seal the test tube with your thumb and invert it in the beaker. Hold the test tube in place with a test tube holder and place the free end of one of the rubber tubes from Step 3 into the inverted test tube. Repeat this procedure for the other rubber tube.

5. Connect each terminal of the battery to one of the electrodes in the Hoffman voltameter. The negative electrode will attract bubbles of hydrogen gas, and the positive electrode will attract bubbles of oxygen gas. Each gas will flow through the rubber tubing and displace the water in the inverted test tubes. Stopper the test tubes once they fill with gas for later use.

References

• Georgia State University: Electrolysis of Water and Fuel Cell Operation

Resources

• Read this Article in Spanish