Ask a Teacher

Search



while studying saponification reaction,a student measures the temperature of the reaction mixture and also find its nature using blue/red litmus paper.on the basis of his observations the correct conclusions would be: a)reaction is exothermic and mixture is acidic b)reaction is endothermic and mixture is acidic c)reaction is endothermic and mixture is basic d)reaction is exothermic and reaction is basic. which type of NaOH is used for Saponification?
Saponification is the hydrolysis of an ester under basic conditions to form an alcohol and the salt of a carboxylic acid. Saponification is commonly used to refer to the reaction of a metallic alkali (base) with a fat or oil to form soap. Saponifiable substances are those that can be converted into soap.

CH2-OOC-R - CH-OOC-R - CH2-OOC-R (fat) + 3 NaOH (or) KOH  both heated ?CH2-OH -CH-OH - CH2-OH (glycerol) + 3 R-CO2-Na (soap)
where R=(CH2)14CH3 in the example (right)

Sodium hydroxide (NaOH) is a caustic base. If NaOH is used a hard soap is formed, whereas when potassium hydroxide (KOH) is used, a soft soap is formed. Vegetable oils and animal fats are fatty esters in the form of triglycerides. The alkali breaks the ester bond and releases the fatty acid and glycerol. If necessary, soaps may be precipitated by salting it out with saturated sodium chloride.

c) is correct. 
This chemical reaction is called saponification. This transformation requires energy brought by heating: the saponification reaction is endothermic. It is Basic because of the presence of alkali.

2. Lye is the common name for sodium hydroxide, also called caustic soda. It is an alkaline substance, meaning it has a pH greater than seven.
    Lye is a white, solid material that can be broken down into flakes, pellets or powder. It is hygroscopic, meaning it absorbs moisture from the air, and exothermic when dissolved in water, meaning it can produce heat.


comments powered by Disqus