Chemical energetics

Flashcards for reviewing key Chemistry concepts, including Hess's Law, enthalpy changes, reaction pathway diagrams, and bond energies.

What does a reaction pathway diagram show?

A reaction pathway diagram shows the energies of the reactants, the transition state(s), and the products of the reaction with time.

What is the transition state in a reaction?

The stage during a reaction at which chemical bonds are partially broken and formed; it's very unstable and higher in energy than reactants and products.

What is activation energy (Ea)?

The minimum amount of energy needed for reactant molecules to have a successful collision and start the reaction.

In an exothermic reaction, how does the energy of the reactants compare to the energy of the products?

The reactants are higher in energy than the products.

How does the activation energy of exothermic reactions compare to endothermic reactions?

Exothermic reactions have a lower activation energy compared to endothermic reactions.

In an endothermic reaction, how does the energy of the reactants compare to the energy of the products?

The reactants are lower in energy than the products.

How does the activation energy of endothermic reactions compare to exothermic reactions?

Endothermic reactions have a higher activation energy compared to exothermic reactions.

Why is energy needed for bond breaking?

Energy (in the form of heat) is needed to overcome attractive forces between atoms.

What happens when new bonds are formed?

Energy is released from the reaction to the surroundings (in the form of heat) when new bonds are formed.

What is bond dissociation energy?

The amount of energy required to break one mole of a specific covalent bond in the gas phase.

What is average bond energy?

An average of a number of the same type of bond but in different environments.

What is specific heat capacity (c)?

The energy needed to increase the temperature of 1 g of a substance by 1°C.