A student carried out experiments using calcium and water. In experiment I, a cleaned piece of calcium of mass 0.6 g was added to 200 cm³ of water: Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g). The volume of hydrogen was measured at intervals and the graph obtained.

1. aState two observations made when calcium reacts with water. [2]
2. bName a substance which could be added to the water to show that a solution containing hydroxide ions has been produced. [1]
3. cState how the rate of reaction changes during the experiment. [1]
4. dExplain why the reaction stops. [1]
5. eHow long does it take for all the calcium to react? [1]

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