question_answer 96)

  Why can dilute solutions of \[{{H}_{2}}{{O}_{2}}\] not be concentrated by heating? How can concentrated solution of \[{{H}_{2}}{{O}_{2}}\]be obtained?

Answer:

  \[{{H}_{2}}{{O}_{2}}\]solution cannot be concentrated by heating beyond30% solution as there is always possibility of explosions. The solution is concentrated at \[35-40{}^\circ C\]under reduced pressure of about 15 mm. Repeated distillation gives 90%\[{{H}_{2}}{{O}_{2}}\]. Further concentration is achieved by cooling with the help of solid \[C{{O}_{2}}\]and ether bath till crystallisation sets in. Crystals are separated, melted and refrozen to get 99% pure\[{{H}_{2}}{{O}_{2}}\].