For preparing soap in the laboratory we require an oil and a base. Which of the following combinations of an oil and a base would be best suited for the preparation of soap?
A. Castor oil and Calcium Hydroxide
B. Turpentine oil and sodium hydroxide
C. Castor Oil and Sodium hydroxide
D. Mustard oil and calcium hydroxide

Hint:We know that the process of making soap is called saponification. A saponification reaction involves the hydrolysis of an ester under acidic conditions or basic conditions and results in the formation of an alcohol and a salt of carboxylic acid or it basically refers to the reaction between metallic alkali and a fat or oil to produce soap.

Complete answer:
As we know that saponification is the process of making soap. A saponification reaction involves the hydrolysis of an ester under acidic conditions or basic conditions and results in the formation of an alcohol and a salt of carboxylic acid or it basically refers to the reaction between metallic alkali and a fat or oil to produce soap.
The metallic alkali used in this process is generally sodium hydroxide and its alkoxide ions acts as a strong base. The oil used is usually a vegetable oil. Let us talk about the given oils, firstly the turpentine oil which is used for medicinal purposes and mustard oil which is used for cooking.
In the case of option, A, that is the Castor oil which makes a stable lather in soap preparation and it is dense and creamy to add the moisturising properties to the soap and Calcium Hydroxide which forms scum which is highly unwanted during the preparation of soap.
In the case of option B, that is Turpentine oil and sodium hydroxide, the turpentine oil has more medicinal purposes but is not suitable.
In the case of option D, that is Mustard oil which is used more for cooking and doesn’t serve the purpose of making soap.
Resulting in castor oil and sodium hydroxide being our best choice.

Therefore the correct answer is (C).

Note:
Turpentine oil has many medicinal uses like it is mixed with animal fat and rubbed on chest or as an inhaler for nasal problems. It is used on wounds and abrasions. In laboratory conditions sodium hydroxide is commonly used as a base and castor oil provides the necessary requirements for soap like moisturising and lather making properties.