5 1 exothermic and endothermic reactions

An exothermic reaction is a reaction that gives out heat energy to the surroundings causing the temperature of the surroundings to increase.

An endothermic reaction is a reaction that takes in heat energy from the surroundings causing the temperature of the surroundings to decrease.

True. Neutralisation reactions are exothermic reactions.

False. Combustion reactions give out energy to the surroundings

The piece of equipment used to measure temperature changes is a thermometer.

True. Temperature will increase in an exothermic reaction.

False. Energy cannot be created or destroyed in chemical reactions.

Cold packs for sports injuries use endothermic reactions to take heat away from the recently injured area.

True. If a reaction transfers energy to the surroundings, the products have less energy than the reactants.

In an endothermic reaction, the temperature of the surroundings decreases as heat energy is absorbed by the system.

Two uses of exothermic reactions are:

False. The reaction of citric acid and sodium hydrogencarbonate is endothermic.

Reaction profiles are graphical representations of the relative energies of the reactants and products in chemical reactions.

A reaction profile show that a reaction is exothermic because the energy of the products is lower than the energy of the reactants.

True. The difference in height between the energy of reactants and products on an energy level diagram represents the overall energy change of a reaction.

An energy level diagram show that a reaction is endothermic because the the energy of the products is higher than the energy of the reactants.

The energy of the reactants and products is displayed on the y-axis of an energy level diagram.

The progress of the reaction is shown on the x-axis of an energy level diagram.

A downwards arrow on an energy level diagram indicates an exothermic reaction.

An upwards arrow on an energy level diagram indicates an endothermic reaction.

A represents the energy level of the reactants.

B represents the progress of the reaction.

C represents the overall energy change of the reaction.

D represents the activation energy of the reaction.

The reaction profile shows an exothermic reaction.

The following reaction profile is for an endothermic reaction.

Activation energy is the minimum energy colliding particles need in order to react.

Bond energy is the amount of energy required to break a bond or the amount of energy given out when the bond is formed.

True. Bond breaking is an endothermic process as energy is needed to break bonds, which is absorbed from the reaction surroundings

False. When new bonds are formed, energy is released which is an exothermic reaction.

True. A reaction is exothermic if more energy is released when new bonds are formed than what was required to break them.

A reaction is endothermic because less heat energy is released forming bonds in the products than is required in breaking bonds in the reactants.

The three steps involved in calculating the enthalpy change using bond energies are:

False. When calculating the energy required to break bonds and that released when new bonds are formed, we do need to consider the number of moles for each substance. The bond energy is multiplied by the number of moles.

The equation used to calculate energy change using bond energies is: energy change = energy taken in - energy given out

The unit of energy change is kJ mol-1.

The type and number of each bond being formed are: