What is the Chemistry of Solutions? NCERT Chemistry Class 12
Chemistry of Solutions – In this article, we will discuss the topic Solution , Types of Solutions and Characteristics of a Solution
A solution is a special type of homogeneous mixture composed of two or more substances.
The substances that make the solution are classified as-
Solute – It is a substance present in a lesser amount, and it is gets dissolved.
Solvent – It is a substance present in a larger amount, and in a solvent, the solute gets dissolved.
Solutes and solvents may be of any form of matter: solid, liquid or gas. The solution has the same physical state as the solvent.
Types of Solutions
If the solvent is a gas, then only gases are dissolved under a given set of conditions. Air (oxygen and other gases dissolved in nitrogen) is an example of a gaseous solution. Since interactions between molecules play virtually no role, dilute gases form rather trivial solutions.
If the solvent is a liquid, then almost all liquids, gases, and solids can be dissolved. Here are some examples:
Gas in liquid – Oxygen in water, Carbon dioxide in water
Liquid in liquid – Alcoholic beverages are generally solutions of ethanol in water.
Solid in liquid – Table sugar (Sucrose) in water, Salt (Sodium chloride (NaCl)) or any other salt in water, which forms an electrolyte: When dissolving, salt dissociates into ions.
Solutions in water are especially common and are called aqueous solutions.
When the liquid solvent involved is not water is called Non–aqueous solutions.
Body fluids are examples for complex liquid solutions, containing many solutes. Many of these are electrolytes since they contain solute ions, such as potassium. Furthermore, they contain solute molecules like sugar and urea. Carbon dioxide and Oxygen are also vital components of blood chemistry, where significant changes in their concentrations may be a sign of severe illness or injury.
If the solvent is solid, then solids, liquids, and gases can be dissolved.
Gas in solids – Hydrogen dissolves rather well in metals, especially in palladium; this is studied as a means of hydrogen storage.
Liquid in solid – Water in solid salt or sugar, Mercury in gold, forming an amalgam, forming moist solids, Hexane in paraffin wax
Solid in solid – Alloys like bronze, brass and many others. Steel, basically a solution of carbon atoms in a crystalline matrix of iron atoms.
Characteristics of a Solution
- A solution is a homogeneous mixture of two or more substances.
- The particles of solute in a solution cannot be seen by the naked eye.
- A solution does not allow beams of light to scatter.
- A solution is stable.
- The solute from a solution cannot be separated by filtration (or mechanically).
- It is composed of only one phase.
ELECTROLYTES & NON-ELECTROLYTES
- Solutions can be characterized by their ability to conduct an electric current. Solutions containing ions are conductors of electricity and those that contain molecules are non-conductors. Substances that dissolve in water to form ions are called electrolytes. The ions formed from these substances conduct electric current in solution.
- Electrolytes are further classified as strong electrolytes and weak electrolytes. In water, a strong electrolyte exists only as ions. Ionic substances such as NaCl are strong
NaCl (s) ————-> Na+ (aq) + Cl–(aq) (only ions present after solution)
- Solutions containing weak electrolytes contain only a few ions. Weak acids and bases that dissolve in water and produce few ions are weak electrolytes.
HF (aq) ————-> H+ (aq) + F–(aq)
- Substances that do not form any ions in solution are called non-electrolytes. With these solutions, the bulb on the conductivity apparatus does not glow. Covalent molecules that dissolve in water but do not form ions, such as sugar, are non-electrolytes.
C12 H22 O11 (s) ————-> C12 H22 O11 (aq) (no ions present after solution)
Solvent is water in the above reaction.
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