Question

: Reaction between calcium oxide and water is a _______ reaction and reaction of mercuric oxide with strong heat is a ________ reaction

Answer 1

Hint : We know that the reaction of water and calcium oxide forms calcium hydroxide. There is more than one way to classify this reaction. These two reactions are very common in chemistry and we can easily find either of them in any chemical reaction. As it can be proposed from their names itself, combination reaction is formation of bonds and decomposition is breaking of bonds.

Complete Step By Step Answer:
Firstly, let us discuss combination reactionsCombination Reaction: It is also known as a synthesis reaction where two or more elements or compounds, known as the reactants, react with each other and combine to form a single compound, called the product. The combination of two or more reactants to give a single product is known as combination reaction.
Combination reactions can be between two different compounds like in the above reaction where magnesium oxide combines with carbon dioxide to give magnesium carbonate. It can also be carried out between two elements or a compound and an element. Decomposition reaction: It is the type of chemical reaction in which a single compound breaks down into two or more elements. These reactions are generally endothermic, as breaking of bond requires a high amount of energy. A simple example of decomposition reaction is hydrolysis of water where a water molecule is broken down into hydrogen and oxygen gas.
The reaction between calcium oxide and water is a combination reaction. The reaction of mercuric oxide with strong heat is a decomposition reaction.

Note :
Remember that it is important to know the difference between exothermic and endothermic reactions. The differentiating factor is heat. In an endothermic reaction, we see that heat is released as a result.