Heptane and water do not mix, and heptane has a lower density (0.684 g/mL) than water (1.00 g/mL)

Question

A 100-mL graduated cylinder with an inside diameter of 3.32 cm contains 33.6 g of heptane and 37.7 g of water. What is the combined height of the two liquid layers in the cylinder? The volume of a cylinder is π r²h, where r is the radius and h is the height.

Answer 1

Firstly, determine the volume occupied by each individual compound, heptane and water respectively:

density = mass / volume → volume = mass / density

vol. of heptane = mass of heptane / density of heptane = 33.6g / 0.684g/mL = 49.12 mL

vol. of water = mass of water / density of water = 37.77g / g/mL = 37.77 mL

Secondly, determine the height of each individual compound in the cylinder:

volume in cylinder = height ⋅ π ⋅ r² → height = volume in cylinder / π ⋅ r²

1. mL = cm³
2. radius (r) = diameter / 2 = 3.32 cm / 2 = 1.66 cm

height of heptane = 49.12 cm³ / π ⋅ (1.66 cm)² = 5.674 cm

height of water = 37.77 cm³ / π ⋅ (1.66 cm)² = 4.363 cm

Lastly, add up the heights for both heptane and water in the cylinder:

height of heptane + height of water = total height

5.674 cm + 4.363 cm = 10.04 cm

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Joseph M.