Question

The liquid substances mercury (density \(=13.5 \mathrm{~g} / \mathrm{mL}\) ), water \((1.00 \mathrm{~g} / \mathrm{mL})\), and cyclohexane \((0.778 \mathrm{~g} / \mathrm{mL})\) do not form a solution when mixed, but separate in distinct layers. Sketch how the liquids would position themselves in a test tube.

Short answer

When mercury (\(13.5~g/mL\)), water (\(1.00~g/mL\)), and cyclohexane (\(0.778~g/mL\)) are mixed in a test tube, they do not form a solution and instead separate into distinct layers based on their densities. The arrangement in the test tube is as follows: 1. Bottom layer: Mercury (highest density, \(13.5~g/mL\)) 2. Middle layer: Water (medium density, \(1.00~g/mL\)) 3. Top layer: Cyclohexane (lowest density, \(0.778~g/mL\)) A sketch of the test tube would show three horizontal layers, with mercury at the bottom, water in the middle, and cyclohexane on the top.

Step-by-step solution

Compare the densities of the liquids

First, let's compare the densities of the three liquids: 1. Mercury: \(13.5~g/mL\) 2. Water: \(1.00~g/mL\) 3. Cyclohexane: \(0.778~g/mL\) From these values, we can see that mercury has the highest density, followed by water, and then cyclohexane.

Arrange the liquids according to their densities

Now that we know the densities, we can arrange the liquids in the test tube according to their densities, from highest to lowest. 1. Bottom layer: Mercury (highest density, \(13.5~g/mL\)) 2. Middle layer: Water (medium density, \(1.00~g/mL\)) 3. Top layer: Cyclohexane (lowest density, \(0.778~g/mL\))

Make a sketch of the test tube with the liquids

With this information about the relative densities of the three liquids, we can now sketch a test tube with the liquids positioned from bottom to top based on their densities. - Draw an upright test tube - Divide it into 3 horizontal layers - Label the bottom layer as "Mercury" (\(13.5~g/mL\)) - Label the middle layer as "Water" (\(1.00~g/mL\)) - Label the top layer as "Cyclohexane" (\(0.778~g/mL\)) This sketch represents the arrangement of the mercury, water, and cyclohexane liquids in a test tube when they are mixed. They form distinct layers, with heavier and denser liquids (mercury) being at the bottom and lighter, less dense liquids (cyclohexane) being at the top.

Key concepts

Mercury

Mercury is a dense, silvery liquid metal that is often recognized by its unique characteristics. In the context of our exercise, it plays a crucial role due to its density, which is much higher than many other substances. With a density of \(13.5~g/mL\), mercury easily sinks below other liquids when layered together.
Understanding mercury's density is essential in comprehending why it settles at the bottom in a mixture with water and cyclohexane. This heavy density indicates that there are more mercury particles packed into a given space, compared to the other liquids. Because mercury doesn't mix with water or cyclohexane, it forms a distinct layer when these are placed together, illustrating its immiscible properties.

Water

Water, known for its vital role in life and nature, is a neutral substance with a density of \(1.00~g/mL\). This makes water denser than cyclohexane but significantly less so than mercury. When mixed with mercury and cyclohexane, water positions itself between the two in a layered arrangement.
In this scenario, water acts as the middle layer. Its molecules are not as tightly packed as mercury, which causes it to sit above the mercury but below the cyclohexane. It's important to note that water does not mix with the other two substances, maintaining its own layer within the test tube.
Interestingly, the density of water is often used as a reference point for measuring other substances, highlighting its role as a benchmarking liquid.

Cyclohexane

Cyclohexane is an organic compound classified as a non-polar solvent. With a density of \(0.778~g/mL\), it is less dense than both mercury and water. This characteristic leads cyclohexane to form the topmost layer when placed with these other liquids in a test tube.
Because cyclohexane is lighter and less dense, it floats above water and mercury, making it the least compact of the three. This immiscibility with water and mercury allows cyclohexane to maintain a clear separation, demonstrating its ability not to mix and forming a distinct layer at the top.

Layer Separation

Layer separation occurs when liquids with differing densities are combined. They do not dissolve into one another but instead separate, creating distinct layers based on their densities.
This phenomenon can be observed with mercury, water, and cyclohexane. Due to their immiscibility and differences in density, they each settle at different levels - mercury at the bottom, water in the middle, and cyclohexane on top. The positioning of these liquids happens naturally due to gravitational forces acting on substances of different masses per unit volume.
The concept of layer separation is a fundamental principle in chemistry and fluid dynamics, helping us understand how substances interact based on density differences.

Test Tube Sketch

A test tube sketch is a simple yet effective way to visually represent the positioning of different liquids based on their densities. When sketching mercury, water, and cyclohexane in a test tube, it's crucial to maintain clarity in their separation.
Start by drawing an upright test tube, then divide it into three horizontal layers. Label the bottom layer as "Mercury" with \(13.5~g/mL\), indicating the densest liquid. Next, label the middle layer as "Water" with \(1.00~g/mL\), followed by the top layer as "Cyclohexane" with \(0.778~g/mL\).
This sketching method clearly demonstrates the concept of layer separation and helps in visualizing the practical outcome of mixing immiscible liquids with varying densities.