Surface tension of water is 72.8mN/m, Hexanol is 24.8mN/m, interfacial tension o
ID: 3307764 • Letter: S
Question
Surface tension of water is 72.8mN/m, Hexanol is 24.8mN/m, interfacial tension of hexanol-water is 6.8mN/m. When hexanol equilibrates with water, the water- air surface tension drops from 72.8 to 28.5. What will happen if a large drop of hexanol is placed at the water-air interface?
Hexanol does not spread on water, but remains as a liquid lens with a definite contact angle
Hexanol initially spreads and then retracts as a liquid lens with time
Hexanol spreads as a monolayer on water
Hexanol dissolves and the lens disappears with time
In-vivo contact angle on human forehead measured immediately after use of a facial cleanser was found to be about 80 degrees. How will the contact angle change after about an hour of exercise?
Contact angle will increase
Contact angle will decrease
Contact angle will not change
Contact angle will become zero
a.Hexanol does not spread on water, but remains as a liquid lens with a definite contact angle
b.Hexanol initially spreads and then retracts as a liquid lens with time
c.Hexanol spreads as a monolayer on water
d.Hexanol dissolves and the lens disappears with time
Explanation / Answer
c. Hexanol spreads and then retracts as a liquid lens with time. on water,as the surface tension of air-water interface reduces, the drop of hexanol which is placed on this surface can spread.
As surface tension reduces, tendency to spread increases, contact angle decreases, but after an hour of exercise salts are produced which increases the surface tension, therefore the contact angle increases
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.