Question

Explain the following terms with examples.
a. Endothermic reaction
b. Combination reaction
c. Balanced equation
d. Displacement reaction

Answer 1

a. Endothermic reaction:
An exothermic reaction is a chemical reaction that releases energy in the form of heat and light. It is the opposite of an endothermic reaction. Exothermic Reaction means "exo" meaning releases and "thermic" means heat. So the reaction in which there is release of heat with or without light is called exothermic reaction.
Expressed in a chemical equation: reactants → products + energy.
For example: Combustion is exothermic reaction.
The chemical reaction between zinc granules and dilute sulphuric acid is exothermic reaction.

b. Combination reaction:
Those reactions in which two or more substances combine to form single substance is called combination reaction
For example: Magnesium and oxygen combine, when heated, to form magnesium oxide.
$2Mg+O_2\to 2MgO$

c. Balanced equation:
A balanced equation is an equation for a chemical reaction in which the number of atoms for each element in the reaction and the total charge are the same for both the reactants and the products. In other words, the mass and the charge are balanced on both sides of the reaction.
The balanced equation is:
2 Fe₂O₃ + 3 C → 4 Fe + 3 CO₂
Both the left and right sides of the equation have 4 Fe, 6 O, and 3 C atoms. When you balance equations, it's a good idea to check your work by multiplying the subscript of each atom by the coefficient. When no subscript is cited, consider it to be 1. It's also good practice to cite the state of matter of each reactant. This is listed in parentheses immediately following the compound. For example, the earlier reaction could be written as:
2 Fe₂O₃(s) + 3 C(s) → 4 Fe(s) + 3 CO₂(g)
where s indicates a solid and g is a gas state of matter.

d. Displacement reaction:
Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Both metals and non-metals take part in displacement reactions.
Chemical reactivity of metals is linked with their relative positions in the activity series.
A metal placed higher in the activity series can displace the metal that occupies a lower position from the aqueous solution of its salt.

For example: