Question

Given a solution of 5.0% by volume oleic acid in alcohol: Two drops (100 drops/cm3) are placed on a water surface and a continuous, circular film is formed 16.0 cm in diameter after all the alcohol has evaporated and the oil is distributed evenly on the surface. What would be the thickness of the layer of pure oil

Answer 1

Thickness = 5.0 * 10^-6 to 1 significant figure

Step-by-step explanation:

Volume of oleic acid added:

2 drops when there are 100 drops per cm³ means that each drop has a volume of;

2 * 0.01 = 0.02 cm³

A 5% v/v oleic acid in solution will contain:

5/100 * 0.02 = 0.001 cm³ of oleic acid .

Area of circular film on the water surface = πr²

where r, radius = 16 /2 = 8cm, π = 3.14

Area = 3.14 * 8²

Area = 201 cm²

Since volume = area * height or thickness

Thickness = volume/area

Thickness = 0.001 cm³ / 201 cm²

Thickness = 0.00000498 or 4.98 * 10^-6 cm

Thickness = 5.0 * 10^-6 to 1 significant figure