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  Teaching Guide

Activity 2: Grades 9-12
Hydrogen Fuel

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  1. Consider the polarity of the ions released when the water decomposed. Which gas collected at the cathode? Why?
    (Oxygen. Oxygen ions are positive and the cathode is negative. Opposites attract.)
  2. Why were there more hydrogen bubbles than oxygen bubbles? (Water contains twice as many hydrogen atoms as oxygen atoms.)
  3. Where did the chlorine gas generated in step 10 come from?
    (Ions of chlorine that had formed when table salt (NaCl) was dissolved in water.)

In addition to generating free chlorine gas, how might adding a "pinch" of salt affect the decomposition of water?
(The salt would make the water more conductive and therefore increase the rate of electrolysis.)

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