Questions & Answers

Sodalime is:
(a) NaOH
(b) NaOH+CaO
(c) CaO
(d) $Na_{ 2 }CO_{ 3 }$

Answer
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Hint: There is no direct formula of soda lime given in the options above. You have to break this word in Soda+lime, then think about the options having Soda and Lime in their formula. Now if you are able to capture this hint you can easily choose the correct option.

Complete step by step answer:
> Let’s discuss all the options one by one to reach our final answer.
- Option A, the compound given is known as sodium hydroxide. It is a strong base. It is also known as caustic soda. Sodium hydroxide is a highly caustic base and alkali that decomposes proteins at ordinary ambient temperatures and may cause severe chemical burns.
- In option B, a mixture of NaOH+CaO is given. This option is correct because soda lime is a granular solid produced by slaking quicklime (CaO) with a concentrated solution of sodium hydroxide, NaOH(aq). Slaking means the hydration of quick lime(CaO) to form $Ca(OH)_{ 2 }$.
- Option C, the compound is calcium oxide. It is commonly known as quicklime or burnt lime, which is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature.
- Option D, the compound is sodium carbonate. It is the inorganic compound with the formula $Na_{ 2 }CO_{ 3 }$ and its various hydrates. All forms are white, water-soluble salts. All forms have a strongly alkaline taste and give moderately alkaline solutions in water.
Therefore, the correct answer to this question is option B.

Note: You should know that a 3:1 mixture of NaOH and CaO is called soda lime.
CaO makes NaOH less reactive. NaOH is quite hygroscopic and forms a sodium hydroxide solution when it is exposed to air. Soda-lime is not that hygroscopic and hence, stabilizes NaOH by avoiding moisture absorption.
In chemical reactions, soda-lime acts as sodium hydroxide but, unlike sodium hydroxide, it is not deliquescent and does not attack the glass.