ANS:B - exothermic

An exothermic reaction is a chemical reaction that releases energy in the form of heat to its surroundings. In an exothermic reaction, the total energy of the products is lower than the total energy of the reactants. This energy difference is released as heat during the reaction. Here's an explanation of key characteristics of exothermic reactions:

1. Energy Change: In an exothermic reaction, the energy released as heat causes the surroundings to warm up. This is because the energy level of the products is lower than that of the reactants, so the excess energy is released into the surroundings.
2. Heat Release: Exothermic reactions often involve the breaking of chemical bonds in the reactants, followed by the formation of new bonds in the products. The energy released when new bonds are formed is greater than the energy required to break the existing bonds, resulting in a net release of energy in the form of heat.
3. Examples: Many common chemical reactions are exothermic, including combustion reactions (such as burning wood or gasoline), neutralization reactions (such as the reaction between an acid and a base to form water and a salt), and some precipitation reactions (such as the formation of solid calcium chloride from aqueous calcium hydroxide and hydrochloric acid).
4. Graphical Representation: On a reaction energy diagram, exothermic reactions are typically represented by a negative change in enthalpy (ΔH < 0), indicating that the reaction releases heat. The energy level of the products is lower than that of the reactants, and the difference in energy is given off as heat.