Lecture 23 - Enthalpy

These flashcards cover key concepts regarding enthalpy, reaction rates, and energy changes in chemical reactions.

What is the equation for internal energy change during a reaction involving heat change and gas volume change?

△Uint = q - p△V

What does a negative q value indicate about a reaction?

The reaction is exothermic.

What is the enthalpy change at constant pressure represented by?

△H = qp

What does a negative △H indicate about a reaction?

The reaction is exothermic.

What is the enthalpy of fusion?

The heat change associated with melting.

What is the enthalpy of combustion?

The heat change associated with completely burning 1 mol of fuel.

What does activation energy (Ea) represent?

The minimum energy required for molecules to react.

According to Hess's Law, what is true about the overall enthalpy of a series of reactions?

It is the sum of the enthalpies, depending only on the initial and final states.

What must occur for molecules to react?

Molecules must collide with correct orientation and sufficient energy.

What is the rate determining step in a chemical reaction?

The formation of the transition state.