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JEE Main levelOne or more correct optionsDifficulty 2 of 3sc135

Which of the following are properties of lyophilic sols?

AThey are reversible: the dispersed phase can be recovered and redispersed by adding the medium again
BThey can be prepared by direct mixing of the substance with the dispersion medium
CThey are coagulated by very small amounts of electrolytes
DThey show a very strong Tyndall effect

Answer: A, B

Lyophilic sols such as starch or gelatin are reversible and form on direct mixing with the medium. Their particles are strongly solvated, so they need large amounts of electrolyte for coagulation, and they scatter light only weakly. The last two statements are therefore wrong.

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