Exothermic and Endothermic Reactions

A student adds a small amount of ammonium chloride to a beaker of water. The temperature of the water decreases from 21⁰C to 17⁰C. Which type of reaction has occurred and why?

• exothermic, heat is released

• exothermic, heat is absorbed

• endothermic, heat is released

• endothermic, heat is absorbed

Which of the following processes is endothermic?

• reacting sodium with water

• the use of petrol in an engine

• distilling crude oil

• burning fossil fuels

In a chemical reactions, bonds in the reactant species are broken and new bonds are formed in the products. which statement is correct?

• bond breaking requires energy, exothermic process

• bond breaking requires energy, endothermic process

• bond breaking releases energy, exothermic process

• bond breaking releases energy, endothermic process

Calcium and hydrochloric acid react to produce calcium chloride and hydrogen gas. The level diagram for the reaction is shown in the picture.

Which statement about this reaction is not correct?

• The temperature of the surroundings increases

• The reaction is endothermic

• The products have less energy than the reactants

• Energy is released during the reaction

The energy level diagram shows the relative energies of the reactantss and products in a reaction.

Which of the following correctly describes the type of reaction and corresponding energy change?

• endothermic, heat is released

• endothermic, heat is absorbed

• exothermic, heat is released

• exothermic, heat is absorbed