Explain with a suitable example, the ...

Explain with a suitable example, the metal used to reduce the following: (a)oxides of less reactive metals. (b)oxides of moderately reactive metals. (c)oxides of highly reactive metal.
  • 1 answers

Meghna Thapar 1 month, 1 week ago

Extraction of Less Reactive Metals:

The less reactive metals are extracted by the reduction of their oxides by heat alone.

Example: Mercury (II) sulphide ore is roasted in air when mercury (II) oxide is formed. When this mercury (II) oxide is heated to about 300° C, it decomposes to form mercury metal.

Extraction of Moderately Reactive Metals:

The moderately reactive metals in the middle of the reactivity series are extracted by the reduction of their oxides with carbon, aluminium, sodium or calcium.

It is easier to obtain metals from their oxides (by reduction) than from carbonates or sulphides. So, before reduction can be done, the ore is converted into a metal oxide. The  concentrated  ores  can  be  converted  into  metal  oxides  by  the  process  of calcination  or roasting.

Calcination is  the  process  in  which  a  carbonate  ore  is  heated  strongly  in  the  absence  of  air  to convert it into a metal oxide.

For example: When  zinc  carbonate  is  heated  strongly  in  the  absence  of  air,  it  decomposes  to  form  zinc oxide and carbon dioxide. Roasting is the process in which a sulphide ore is strongly heated in the presence of air to convert it into a metal oxide.

 

Extracting Metals towards the Top of the Activity Series:

Metals high up in the reactivity series are very reactive. These metals have a strong affinity for oxygen.  So, oxides of sodium, magnesium, calcium  and aluminium cannot be reduced by carbon.

These metals are obtained by electrolytic reduction.

Sodium, magnesium and calcium are obtained by the electrolysis of their molten chlorides.

Example: Sodium metal is extracted by the electrolytic reduction of molten sodium chloride. When electric current is passed through molten sodium chloride, it decomposes to form sodium metal and chlorine gas.

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