Heat Capacity Of Ionic Compounds


The heat capacity of a substance can be defined as the amount of heat required to change its temperature by one degree. A more useful quantity is specific heat capacity, which is the amount of heat required to change the temperature of one unit mass of a material by one degree. Heat capacity is a fundamental property of any material. Simply the heat capacity of a substance is the amount of heat required to change its temperature by one degree.

A solution of an ionic compound in water conducts electricity and undergoes a chemical reaction. Lattice energy is the force that holds ions together in an ionic compound. Solubility of Ionic Compounds in Water at 25°C depends on the size and charge of the ions in the compound. Stronger ionic bonds occur when the ions are smaller and the ions carry multiple charges. Water is used as a solvent, and in many chemical reactions heat is given out as a byproduct; water which has a high heat capacity can absorb this heat.

Rules for Naming Ionic Compounds

The names and formula of ionic compounds can be determined by simple rules. The rules for simple ionic compound composed of one metal and one non-metal are given below.

The Naming rules are

  • Name the metal first.
  • Name the non-metal second.
  • Delete the last few letters of the non-metals name and substitute ‘ide’.

The valency rules are

  • The chemical formula of an ionic compound can be determined using valency rules.
  • Each metal and non-metal is assigned a valency.
  • The valency is the combining power of the element.
  • The valency of a metal is equal to the charge on its cation.
  • The valency of a non-metal is equal to the charge on its anion.
  • In an ionic compound the total positive charge of the cations must equal the total negative charge of the anions.

Heat Capacity of Water

When a given body is heated, it absorbs a certain amount of heat energy for 1oC in its temperature. The heat energy thus absorbed by it is known as its heat capacity. Heat capacity is not a fixed quantity and it depends upon the mass of a substance. The heat capacity increases with increase in the mass of the substance. Water is one of the liquids having high heat capacity. The S.I unit of heat capacity is joule per kelvin.

The advantages of high specific heat capacity of water are formation of sea and land breezes, use of water for fomentation, water as coolant and use of water in the internal heating of buildings. Water can absorb a large amount of heat energy, without its temperature becoming too high. This property of water makes it a good coolant. For fomentation, hot water is used in bottles since water can store a large amount of heat energy at relatively low temperature due to high specific heat capacity.

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