Take hot water and cold water in two test tubes. Add one drop of phenolphthalein to both of the test tubes. Then add magnesium ribbon of the same size to this test tubes.
a) Which test tubes shows the sudden formation of pink colour?
b) What is the reason for the sudden formation of pink colour?
c) Which gas is formed?
d) Write the equation for the chemical reaction.

Explanation

a) Pink colour is formed rapidly in hot water.
b) Rate of the chemical reaction depends on temperature . Kinetic energy of the molecule increases on heating. As a result the rate chemical reaction increases which makes the sudden formation of pink colour.
C) Hydrogen
d) `Mg(s) + 2H_2 O (l) rarr Mg(OH)_2 (aq) + H_2(g)