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# Saturated and Unsaturated Solutions

A saturated solution is one that contains the maximum amount of solute capable of being dissolved, whereas unsaturated solutions contain less than the maximum amount of solute capable of being dissolved. Because carbonated water is saturated with carbon, it emits carbon through bubbles. Sand in water is an example of an unsaturated.

### Saturated Solutions

A saturated solution is a chemical solution that contains the greatest quantity of solute contained in the solvent. The solute cannot be dissolved anymore in a saturated solution.

The saturation point of any liquid is determined by the type of the material and the temperature. A saturated solution is one in which the quantity of dissolved solute equals the saturation point of the solvent. A solvent can dissolve some particular types of solutes in it.

The maximum amount of solute that can be dissolved in a solvent at a specified temperature can be termed as a saturated solution. A solution cannot dissolve any more solute further upon reaching saturation. The undissolved substances remain at the bottom. The point at which the solute stops dissolving in the solvent is termed the saturation point.

Following are the examples of Saturated Solutions:

• Soil is a saturated mixture consisting of nitrogen. On attaining the saturation point, the excess nitrogen is emitted out into the air in the form of gas.
• Beverages, such as cold drinks are saturated solutions of dissolved carbon in water.
• Protein drinks which is a saturated solution of protein powder in milk etc.

### Unsaturated Solutions

A solute must be added to a solvent in order for a solution to form. At first, the solute dissolves in a solvent and forms a homogeneous solution. A solution in which solutes dissolve is referred to as an unsaturated solution. A solution is made up of two types of particles: solutes and solvents. Water is commonly used as a solvent (which is one of the reasons why water is also called the universal solvent).

Unsaturated solutions have the ability to dissolve additional solute until they achieve saturation. Solutes will no longer dissolve in the solvent after reaching the saturation threshold, resulting in unsaturated solutions.

As a result, all solutions are considered to be largely unsaturated in nature before being transformed into saturated solutions by adding solute to them. The amount of solute that is contained in lesser amounts than the maximum value, that is before the solution reaches the saturation level is called an unsaturated solution. No remaining substances leave at the bottom, that is, all the solute is dissolved in the solvent. An unsaturated solution is basically a chemical solution that has a solute concentration lesser than its corresponding equilibrium solubility.

Following are the examples of Unsaturated Solutions:

• Salt or sugar dissolved in water below the saturation point.
• Air or mist.
• Iced coffee.
• Vinegar is the acetic acid solution in water.

### Interconversion of Saturated and Unsaturated Solution

Saturated solution on heating becomes unsaturated whereas an unsaturated solution becomes saturated upon cooling. On heating the saturated solution, the solubility of that particular solute increases in the given solvent. As a result of this, more solute can be dissolved into the solvent. However, in the case of cooling a solution, the solute particles which were initially dissolved in the solvent separate out as crystals.

### Solubility

The amount of the solute present in the saturated solution at the given temperature can be termed as the solubility of the solute in the solvent.

The maximum amount of a solute that can be dissolved in 100 gm of a solvent. Different solutes possess varying different solubilities. Solubility increases with an increase in temperature. In the case of saturated solutions, the solute concentration is equivalent to the equilibrium solubility. The solubility of a substance depends on the solvent. It is observed that sugar dissolves in water but not in oil.

Effect of Temperature and Pressure on Solubility

1. The solubility of solids in liquids typically increases as temperature rises and decreases as temperature falls.
2. The solubility of solids in liquid is unaffected by pressure variations.
3. The solubility of gases in liquids typically decreases as temperature rises and rises as temperature falls.
4. Gas solubility in the liquid increases with rising pressure and decreases with lowering pressure.

### Concentration of Solution

The quantity of solute present in a specified quantity of the solvent can be termed as the concentration of the solution. It is measured as a fraction of the amount of solute dissolved in a given mass or volume of a solvent.

A solution in which less amount of solute is present is called a dilute solution whereas, a solution containing more solute is called a concentrated solution.

Mathematically,

• Concentration of solution = Amount of Solute / Amount of Solvent

Also,

• Concentration of solution = Amount of Solute / Amount of Solution

### Sample Problems

Problem 1: A solution is formed by dissolving 20g of sodium chloride in 180 g of water as solvent. Compute the concentration of the solution.

Solution:

Given,

Mass of sodium chloride = 20 g

Mass of water = 180 g

We know,

Mass of solution = Mass of solute + Mass of solvent

= 20 g + 180 g

= 200 g

Concentration of solution is given by,

= [(Mass of solute)/ (Mass of solution)] × 100

= (20/200) × 100

= 10 %

Problem 2: How to identify whether the solution is saturated or not?

Solution:

We take a solution with a solute dissolved in the solvent. On constant stirring, if more solute can be dissolved into the solvent, then the solution is unsaturated otherwise saturated.

Problem 3: How can you create a saturated solution?

Solution:

Following are the steps to create a saturated solution:

• Adding a solute to a solvent beyond the point that solid gets dissolved in the solvent.
• Adding seed crystals to a supersaturated solution.
• Evaporating a solvent from a solution till the point the solute in the solution begins to crystallize or precipitate.

Problem 4: Give some outdoor examples of saturated solutions.

Solution:

Some of the outdoor examples of saturated solutions are:

1. Seawater – A saturated solution with salt as the solute.
2. Soil – A saturated solution with nitrogen.
3. Air – A saturated solution with moisture.
4. Freshwater – Water containing elements and metals, like potassium, dissolved till saturation.

Problem 5: Give one example to show a solution that can be unsaturated, saturated, and supersaturated at different intervals of time.

Solution:

Considering a soda bottle can show that a solution can be unsaturated, saturated, and supersaturated at different intervals of time. Before opening the soda bottle, the solution is supersaturated, On opening the bottle, the excess dissolved carbon dioxide escapes from the surface resulting in the formation of bubbles. This is a saturated solution. When left for a large amount of time, the soda water goes flat and turns into an unsaturated solution.

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