SO 2MgO + S XII XII - - - - Reducing property: As it can readily be oxidised, it acts as a reducing agent. It reduces chlorine into hydrochloric acid. SO + 2H O + Cl H SO + 2HCl It also reduces potassium permanganate and dichromate to Mn + and Cr + respectively. 2KMnO + 5SO + 2H O K SO + 2MnSO + 2H SO K Cr O + 3SO + H SO K SO + Cr (SO ) + H O Reaction with oxygen: Sulphur dioxide is oxidised to sulphur trioxide upon heating with oxygen at high temperature.
This reaction is used for the manufacture of sulphuric acid by contact process. 2SO (g) + O (g) 2SO (g) V O C → Bleaching action of sulphur dioxide: In presence of water, sulphur dioxide bleaches coloured wool, silk, sponges and straw into colourless due to its reducing property. SO + 2H O H SO + (H) X + (H) XH Coloured Col ourless However, the bleached product (colourless) is allowed to stand in air, it is reoxidised by atmospheric oxygen to its original colour. Hence bleaching action of sulphur dioxide is temporary.
Uses: . Sulphur dioxide is used in bleaching hair, silk, wool etc... . It can be used for disinfecting crops and plants in agriculture.
Structure of sulphur dioxide: In sulphur dioxide, sulphur atom undergoes sp hybridisation. A double bond arises between S and O due to pπ- dπ overlapping. . .
Sulphuric acid: (H SO ) Preparation: Sulphuric acid can be manufactured by lead chamber process, cascade process or contact process. Here we discuss the contact process. Manufacture of sulphuric acid by contact process: The contact process involves the following steps. i.
Initially sulphur dioxide is produced by burning sulphur or iron pyrites in oxygen/air. Figure . Structure of sulphur dioxide. XII XII - - - - S + O SO 4FeS + 11O 2Fe O + 8SO ii.
Sulphur dioxide formed is oxidised to sulphur trioxide by