What are the general steps to solve a Hess's Law problem?
1. Identify target equation. 2. Manipulate given equations (reverse, multiply) to match target. 3. Add manipulated equations and their ฮH values.
What happens to ฮH when reversing a reaction in Hess's Law?
The sign of ฮH is changed (positive becomes negative, and vice versa).
What happens to ฮH when multiplying a reaction by a coefficient in Hess's Law?
ฮH is also multiplied by the same coefficient.
What do you do with the ฮH values after manipulating the equations?
Add all the manipulated ฮH values together to obtain the overall ฮH for the target reaction.
What should be done after manipulating the equations and adding them together?
Cancel out any spectator species that appear on both sides of the equation to obtain the final target equation.
Define 'state function'.
A property whose value does not depend on the path taken to reach a specific state, only on the initial and final states.
What does 'pathway dependent' mean?
A process or function that depends on the specific route taken. The result changes if a different path is taken.
What does 'pathway independent' mean?
A process or function that does not depend on the specific route taken. The result is the same no matter which path you choose.
Define enthalpy (H).
A thermodynamic property of a system that is the sum of the internal energy of the system plus the product of pressure and volume.
Define Hess's Law.
The enthalpy change for a reaction is independent of the path taken; it's a state function.
Compare and contrast pathway-dependent and pathway-independent functions.
Pathway-dependent: Value depends on the route taken. | Pathway-independent: Value depends only on initial and final states, not the route.
What is the difference between enthalpy and work in terms of state functions?
Enthalpy: Is a state function, depends only on initial and final states. | Work: Is not a state function, depends on the path taken.
