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Question
Explain the following.
Lithium floats and water while sodium floats and catches fire when put in water.
Solution
- When lithium and sodium react with water, hydrogen gas is released. Due to these hydrogen gas bubbles, lithium and sodium float on water.
eg. \[\ce{2Na + 2H2O->2Na+ + 2OH^- + H2 ^}\] - The reactivity of group 1 metals increases with increasing atomic radius and lowering of ionization enthalpy down the group.
- Thus, sodium having lower ionization enthalpy is more reactive than lithium.
- Hence, lithium reacts slowly while sodium reacts vigorously with water.
- Since the reaction of sodium with water is highly exothermic, it catches fire when put in water.
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