UNIT NO.7
Solutions
(Solved Exercise)
7.2 Define the followings:
1. Binary solution
A solution, which is prepared by mixing only two substances, is called a binary solution.
For example solution of salt and water.
2. Aqueous solution
A solution in which water is used as a solvent is called aqueous solution (aqua means water).
3. Solute
The solute is a substance that dissolves. In a binary solution, solute is that component of the solution which is present in smaller quantity. e.g. Ina 5% sugar solution in water, sugar is the solute.
4. Homogeneous mixture
A homogenous mixture is that mixture in which the components mix with each other and its composition is uniform throughout the solution. For example Saltwater (Salt dissolved evenly in water).
5. Unsaturated solution
Such a solution to which further amount of the solute can also be dissolved at a particular temperature is called unsaturated solution.
7.3 Constructed Response Questions
1. Describe preparation of a solution.
preparation of a solution is an easy process. When a teaspoon of sugar is added to a glass of water and stirred, sugar dissolves in water producing a homogeneous mixture. This homogeneous mixture is called a solution. So our solution is prepared.
2. Describe the factors affecting the solubility.
Following are the factors that affect solubility:
• Nature of the solute and solvent
• Temperature of the solution.
• Pressure.
Nature of solute and solvent
The principle of dissolution is that like dissolves like. Water has ionic character. The ionic compounds like sodium chloride, silver nitrate, silver chloride, etc. are dissolved in water. The covalent compounds are dissolved in covalent solvent.
Temperature
Generally, an increase in temperature of the solution increases the solubility of a solid solute. For example, greater amount of sugar is dissolved in hot water than in cold water. Solubility of gases decreases with the increase in temperature of the solution. For example, solubility of carbon dioxide in soda water decreases when temperature increases.
Pressure
Pressure affects the solubility of gaseous solutes in liquid solvents. Carbon dioxide is dissolved in soda water. When the cap on the soda bottle is opened, the pressure on the solution is released and carbon dioxide dissolved under pressure begins to bubble out.
3. Explain the effect of temperature on the solubility of table salt in water.
Generally, an increase in temperature of the solution increases the solubility of a solid solute. For example, greater amount of salt is dissolved in hot water than in cold water. So solubility of table salt in water is increased when temperature increased.
4. Describe the importance of solutions in daily life.
Importance of solutions/Solubility in Daily Life
There are many practical applications of solutions or solubility in daily life, especially in industries. A few are mentioned below:
1. In carbonated drinks, carbon dioxide remains dissolved in water due to its solubility in water.
2. Paints are dissolved in the solvents like alcohol and ether, etc. These solvents help to dry the paint.
3. Water soluble dyes are used in textile industry on greater scale as dyes (coloured substances) are used to create colourful patterns on clothes.
4. Solubility is very important in pharmaceutical industry. It is helpful to achieve the desired concentration of the drugs in solutions.
5. Use of solubility parameters is very important in petroleum industry.
5. How can we increase the process of dissolution?
Size of the solute particles, stirring the solution and the temperature, etc., are the ways used to accelerate the process of dissolving materials.
7.4 Investigate the importance of solubility in textile and pharmaceutical industries.
Solubility is very important in pharmaceutical industry. It is helpful to achieve the desired concentration of the drugs in solutions.
Water soluble dyes are used in textile industry on greater scale as dyes (coloured substances) are used to create colourful patterns on clothes.