Oils Fats and Soaps Questions and Answers

Answer: C

Three moles of the alkali of mass fifty-six saponify one mole of triglyceride, so the molecular weight is three times fifty-six thousand divided by one hundred and ninety. A high saponification value therefore means short chains.

Answer: D

Both are true and the reason gives the inverse relation: coconut oil with its short chains has a high value while a long chain oil such as rapeseed has a considerably lower one. The relation is inverse rather than direct.

Answer: A

Adding hydrogen across the double bonds converts a liquid oil into a plastic fat suitable for margarine and shortening. The stability improves because the double bonds that oxidise are removed. Selectivity of the catalyst controls the texture obtained.

Answer: B

Correct answer: finely divided nickel

Nickel on a support is the standard hydrogenation catalyst for edible oils: it is active enough at moderate temperature and pressure, cheap, and filterable from the finished oil. The selectivity is controlled through temperature, pressure and agitation, since the conditions determine both how far the hydrogenation goes and how much trans isomer is formed along the way.

Answer: C

Isomerisation of cis double bonds accompanies the addition, which is why partially hydrogenated fats have been restricted in many countries. Full hydrogenation or interesterification is used instead in modern practice.

Answer: D

Deodorisation removes volatiles and does not change the melting behaviour at all. The other three are the three routes actually used to build a fat of the required consistency. Blending is the simplest of the three routes.

Answer: A

The ester links are hydrolysed and the acids are neutralised in one step, releasing the glycerol backbone. Glycerine recovery from the spent lye is a significant part of the value of a soap plant. The reaction is a hydrolysis and a neutralisation together.

Answer: B

The first two are correct. The third is the wrong way round, since potassium soaps are the soft ones used in liquid and shaving products while sodium soaps make hard bars. The choice of alkali decides the product form.

Answer: C

Correct answer: hydrogenation over nickel

Hydrogenation belongs to oil processing, not to soap making - it saturates double bonds in the oil before any soap is made. The kettle process itself is saponification with caustic, graining out with salt to separate the soap from the glycerine-bearing lye, and fitting to give a clean layer of neat soap above the spent lye.

Answer: D

The scum both wastes soap and deposits on fabric and fittings. Synthetic detergents were developed largely because their calcium salts remain soluble. The scum is both a waste and a nuisance. Softening the water restores soap performance.