All Flashcards
What are the general steps to solve a Hess's Law problem?
- Identify target equation. 2. Manipulate given equations (reverse, multiply) to match target. 3. Add manipulated equations and their ΔH values.
What happens to ΔH when reversing a reaction in Hess's Law?
The sign of ΔH is changed (positive becomes negative, and vice versa).
What happens to ΔH when multiplying a reaction by a coefficient in Hess's Law?
ΔH is also multiplied by the same coefficient.
What do you do with the ΔH values after manipulating the equations?
Add all the manipulated ΔH values together to obtain the overall ΔH 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.
What is the effect of reversing a reaction on the sign of ΔH?
Reversing a reaction changes the sign of ΔH (positive becomes negative, and vice versa).
What is the effect of multiplying a reaction by a factor 'n' on the value of ΔH?
ΔH is also multiplied by the same factor 'n'.
What is the result of adding multiple reactions together in Hess's Law?
The corresponding ΔH values are added together to give the overall ΔH for the net reaction.
What happens if you forget to change the sign of ΔH when reversing a reaction?
The calculated enthalpy change for the overall reaction will be incorrect.
What happens if the final equation does not match the target equation when using Hess's Law?
The calculated enthalpy change will be incorrect, indicating an error in the manipulation or cancellation of species.
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.