Soda lime is a mixture of which of the following?

Soda lime is an important chemical mixture composed primarily of calcium oxide (CaO) and sodium hydroxide (NaOH). It is a dry, granular substance that serves multiple purposes in both laboratory and industrial chemistry. The combination of CaO and NaOH creates a strong base mixture that is capable of absorbing carbon dioxide and removing acidic impurities from gases or chemical reactions.

In organic chemistry, soda lime plays a key role in the decarboxylation reaction, which involves the removal of a carbon dioxide (CO₂) molecule from the sodium salt of a carboxylic acid to produce an alkane. For example:

RCOONa + NaOH → RH + Na₂CO₃
(This reaction is carried out by heating the mixture with soda lime.)

Here, NaOH acts as the active chemical reagent that reacts with the sodium salt of the carboxylic acid, while CaO acts as a drying agent to keep the reaction medium water-free and prevent the NaOH from becoming diluted or inactive. The presence of CaO ensures that the reaction mixture remains solid and that the reaction proceeds smoothly upon heating.

Beyond organic chemistry, soda lime has vital practical uses:

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  It is used in breathing equipment, submarines, and diving apparatus to absorb CO₂ exhaled by humans.

  
  


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  It is utilized in medical anesthesia machines to maintain clean, CO₂-free air for patients.

  
  


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  In laboratories, it helps maintain controlled environments by removing CO₂ from reaction vessels.

  
  

Chemically, the CO₂ absorption process can be represented as:
CO₂ + Ca(OH)₂ → CaCO₃ + H₂O

Thus, soda lime (CaO + NaOH) serves as both a powerful base and an efficient CO₂ scrubber, making it a highly valuable reagent in organic synthesis and gas purification systems.

Key Facts:

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  Composition: CaO + NaOH

  
  


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  Main use: Decarboxylation of carboxylic acids

  
  


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  Additional use: CO₂ absorption in closed systems

  
  


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  Appearance: White granular solid, highly hygroscopic