Surfactants

Question 1

What is the surfactant number?

Answer 1

The ratio of the hydrocarbon chain area, ahc, to the head group ahg. This ratio is important to the self assembly of amphipholes

Question 2

What surfactant numbers indicate a spherical assembly of amphiphiles?

Answer 2

P<1/3

Question 3

What surfactant numbers indicate a vesicle assembly of amphiphiles?

Answer 3

1/2<P<1

Question 4

What surfactant numbers indicate a worm assembly of amphiphiles?

Answer 4

1/3<P<1/2

Question 5

What surfactant numbers indicate a bilayer assembly of amphiphiles?

Answer 5

P- 1

Question 6

How is CMC mainly determined?

Answer 6

CMC is mainly determined by the nature of the surfactant and the chain length

Question 7

What is the effect on CMC when chain length is increased?

Answer 7

Decreases exponentially as the chain length increases

Question 8

How to measure surface tension?

Answer 8

De nuoy ring, Wilhelmy plate, Bubble pressure tensiometer

Question 9

What is the young-laplace equation?

Answer 9

The Young-Laplace equation describes the pressure difference across a curved interface between two fluids due to surface tension. It relates the pressure difference to the surface tension and the curvature of the interface. Essentially, it explains why there’s a higher pressure inside a soap bubble than outside.

Question 10

How to surfactants lower surface tension?

Answer 10

by adsorbing at the air-water interface and forming a monolayer. This monolayer lowers the cohesive forces between liquid’s molecules, and as a result, the surface tension is lowered.

Question 11

What is the structure of a surfactant?

Answer 11

Surfactants have a polar (hydrophilic) head that attracts water and a nonpolar (hydrophobic) tail that repels water.

Question 12

Why is the structure of a surfactant important?

Answer 12

This dual nature causes surfactants to preferentially accumulate at the interface between a liquid (like water) and another medium (like air or oil).

Question 13

What do surfactants to do decrease surface tension?

Answer 13

At the interface, the hydrophilic heads interact with water molecules, while the hydrophobic tails point towards the other medium. This disrupts the strong hydrogen bonds and other cohesive forces that water molecules have with each other, thus lowering the surface tension.