Heptane and water do not mix, and heptane has a lower density (0.684 g/mL.) than water (1.00 g/ mL). A 100-ml graduated cylinder with
an inside diameter of 3.08 cm contains 37.8 g of heptane and 34.7 g of water. What is the combined height of the two liquid layers in
the cylinder? The volume of a cylinder is r’h, wherer is the radius and h is the height.
cm

Explanation:

volume of heptane= mass / density

volume of heptane = 37. 8 / .684

= 55.26 mL

volume of water  = 34.7  / 1

= 34.7 mL or cc.

If l₁ be the length of heptane layer in the graduated cylinder

volume = cross sectional area x length or height  of layer

π r² x l where r is radius of bore of the cylinder  , l is height of liquid inside cylinder .

for heptane

π r² x l₁ =  55.26

3.14 x 1.54² x l₁ = 55.26

l₁ = 7.42 cm

for water

π r² x l₂ =   34.7

3.14 x 1.54² x l₂ = 34.7

l₂ = 4.65  cm

Combined height = l₁ + l₂

= 7.42 + 4.65

= 12.07 cm .