Page 204 - ICSE Chemistry 8
P. 204

Activity 9.3


                 Aim: To show that wood charcoal is a good adsorbent
                 Materials required: A gas jar, some hydrogen sulphide gas, some wood                          hydrogen
                 charcoal                                                                                      sulphide gas
                 Procedure

                   •  Take a gas jar and fi ll it with hydrogen sulphide gas. It gives a pungent
                       smell.
                   •  Put some charcoal pieces in the jar and close the lid.                                       charcoal

                   •  Shake the jar and leave it s  ll for some   me.
                   •  Remove the lid and smell.
                 Observa  on: The pungent smell given out by hydrogen sulphide is no longer there.

                 Conclusion: This shows that charcoal is a good adsorbent.



                 Uses of Wood Charcoal                                                    Diff erence between Adsorp  on

                     •  Wood charcoal is widely used as a fuel. It is a be  er fuel               and Absorp  on
                        than wood due to the following reasons.                          Adsorp  on is the surface reten  on
                                                                                         of molecules of a liquid, gas or a
                         (i) Its igni  on temperature is lower than that of wood.        solu  on by a solid or liquid. On

                         (ii)  It has higher calorifi c value than that of wood.          the other hand, absorp  on is the
                                                                                         penetra  on of substances into the
                         (iii)  It produces no smoke, i.e., causes less air pollu  on than   bulk of the solid or liquid.
                             wood.

                     •  It is used as a reducing agent in the extrac  on of metals from their metallic oxides.

                     •  Since it has a high adsorbing capacity, it is used in gas masks for military and industrial purposes.
                     •  It is a cons  tuent of gunpowder which is an explosive used in guns and rifl es.
                     •  Because it adsorbs coloured materials also, it is used as a decolourising agent in sugar solu  ons.

                     •  It is used to prepare an  -gastric tablets that are used by people suff ering from indiges  on and
                        gastric problems.

                     •  It is used to prepare deodorants as it also adsorbs foul-smelling gases.
                     •  It is used in making fi lters and sieves.


                 Activated Charcoal

                 Ac  vated charcoal is formed by hea  ng wood charcoal at around 900°C in limited supply of air. In powdered
                 form, ac  vated charcoal has more surface area than that of wood charcoal. It is therefore more eff ec  ve
                 and more widely used as an adsorbent.

                 Ac  vated charcoal is used as a catalyst in various chemical reac  ons. It is also used to separate a mixture
                 of noble gases.



                  190
   199   200   201   202   203   204   205   206   207   208   209