JEE Advanced levelSingle correct optionDifficulty 3 of 3sc208
An oil-in-water emulsion is stabilised by sodium stearate. Dilute hydrochloric acid is added in excess and the emulsion breaks. The best explanation is:
Astearate is converted to the water-insoluble stearic acid, so the emulsifying film is destroyed
Bthe acid converts the oil-in-water emulsion into a true solution
Cthe acid dissolves the oil droplets
Dthe chloride ions increase the interfacial tension between oil and water
Answer: A
The emulsifier is CX17HX35COO−NaX+. With excess strong acid it forms CX17HX35COOH, which is insoluble in water and no longer sits as an ionic film at the interface. Without the film the droplets coalesce and the emulsion breaks.