Question

What type of chemical reaction takes place when i) limestone is heated?
ii) a magnesium ribbon is burnt in air?

Answer 1

Hint: A chemical reaction happens when one or two substances undergo a chemical change that produces new products. There are various types of chemical reactions like combination, decomposition, displacement, neutralization reactions. These may involve various or few reactants to produce chemical changes.

Complete answer:
A chemical reaction is a process that enables certain chemical compounds to react together and make new compounds, or to convert into new compounds. There are various types of reactions like combination, decomposition, displacement, double displacement, redox, and neutralization reactions.
We have been given two cases where limestone is heated, and a magnesium ribbon is burnt in air. The reactions will be:
i)Limestone is heated, limestone is calcium carbonate $CaC{{O}_{3}}$that on heating produces two compounds, calcium oxide and carbon dioxide as
$CaC{{O}_{3}}\xrightarrow{\Delta }CaO+C{{O}_{2}}$ , as two products are being formed from a single reactant, it means it is a type of decomposition reaction.
ii) a magnesium ribbon is burnt in air, when a magnesium ribbon that is pure magnesium, burns in air, it reacts with oxygen and forms magnesium oxide MgO, the reaction is
$2Mg+{{O}_{2}}\to 2MgO$ , as from the combining of Mg and oxygen magnesium oxide is formed, it is a type of combination reaction.
Hence, the type of chemical reaction when limestone is heated is decomposition reaction and when magnesium ribbon is burnt in air is a combination reaction.

Note:
A combination reaction involves 2 reactants to combine together to form a single product. A decomposition reaction involves a single reactant to decompose and form two products. While a displacement reaction involves a more reactive element from the reactants, displacing the less reactive element from the aqueous salt solution, and neutralization is a reaction between acid and a base that forms a salt.