6. Chemical Energetics Flashcards
What do the terms exothermic and endothermic mean
Endothermic - a reaction that takes in heat energy from the surroundings
Exothermic - a reaction that give out energy to the surroundings
Give an example of a type of reaction that is exothermic
Combustion
Neutralization
Give an example of an endothermic reaction
Thermal decomposition
Photosynthesis
In terms of bond energies what happens during a chemical reaction
Energy is needed to break bonds and is released when bonds are made
Exothermic - energy released from making bonds is greater than the energy used to break bonds
Endothermic - energy required to break bond is greater than the energy released when making bonds
Mexo
Bendo
What is a reaction profile
A graph which shows the relative energies of reactants and products as well as the activation energy of the reaction
Draw a reaction profile for an endothermic reaction
Draw a reaction profile for an exothermic reaction
Label the following reaction profiles as exothermic or endothermic
How can the energy change of a reaction be calculated from bond energies
Energy change (kJ molˆ-1) = total energy of bonds broken - total energy of bonds made
If the energy change of a reaction is negative, is the reaction exothermic or endothermic
Exothermic
Energy has been lost to the surroundings
Fill in the gap
Fuels are burned to resales ___ ___
Heat energy
Which colourless gas can be used as a fuel
Hydrogen
What is a fuel cell
A cell that continually produces a voltage as long as it is supplied with oxygen and a fuel
What is the only product of a hydrogen-oxygen fuel cell
Water
Write an equation for the overall reaction that takes place in a hydrogen-oxygen fuel cell
2H2 + O2 —> 2H2O
