Electrolysis of water

(water => hydrogen and oxygen)

When an electric current is passed through water, water molecules break apart to form its constituent elements, namely hydrogen and oxygen gasses.

The apparatus used for the electrolysis of water is shown on the right. Hydrogen gas is produced at the negative terminal while oxygen gas is produced at the positive terminal. Click to see the chemical reactions that occur at each electrode.

Solar electricity can be harnessed to break water into hydrogen and oxygen. These gases can later be used in a fuel cell to produce electricity.

View the video on the right.

What is the ratio of the volume of hydrogen produced compared to oxygen?
Explain why this ratio exists with reference to the chemical equation below.

2H2O(l) => 2H2(g) + O2(g)

Notice how each gas is collected.
Why is hydrogen allowed to rise into the collecting test tube?


Why is oxygen allowed to sink into the collecting test tube?


Which of the following is a property of hydrogen gas?

Describe a way that solar energy can be collected and stored on a Martian base and used during night time.

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