Exothermic and endothermic reactions：练习题

Which statement correctly describes an exothermic reaction?

What is the correct definition of activation energy, \(E_a\)?

Which statement explains the energy change in a reaction in terms of bond breaking and bond making?

Which of the following processes is endothermic?

A student adds a solid to a beaker of water. The temperature of the water changes from \(21^\circ\text{C}\) to \(15^\circ\text{C}\).
Which row correctly describes this reaction?

State what happens to the temperature of the surroundings during an endothermic reaction and explain why this change occurs.

Explain what the term enthalpy change, \(\Delta H\), represents and identify its sign (positive or negative) for an exothermic reaction.

In a reaction pathway diagram, the products are located at a higher energy level than the reactants. Identify the type of reaction and determine if the enthalpy change, \(\Delta H\), is positive or negative.

A student adds a spatula of ammonium nitrate to a beaker containing 50 cm\(^3\) of water. After stirring, the temperature of the water decreases by 5 °C.

(a) State whether the reaction is exothermic or endothermic.
(b) Describe the transfer of thermal energy between the reaction mixture and the surroundings.

The diagram for a reaction shows the energy level of the reactants at 100 kJ/mol and the products at 250 kJ/mol. The highest point on the curve (peak) is at 400 kJ/mol.

(a) Determine the enthalpy change, \(\Delta H\), for this reaction.
(b) Determine the activation energy, \(E_a\), for this reaction.
(c) State, with a reason, whether this reaction is exothermic or endothermic.