Chapter 4 (thermochem)

Question 1

How to use the heats of the products to find the final heat.

Answer 1

1. Get the heats of the items in the products, and reactants. (Usually given)
2. Plug into this formula. (Sum of products-sum of reactants. )
3. If a chemical is doubled, it’s heat must be doubled as well.

Question 2

An element in its natural state has a heat of formation of

Answer 2

0 forever and always

Question 3

How to use bond energy to solve for the enthalpy change.

Answer 3

1. Look at the Louis structure for the equation.
2. Look at the chart for each bond, and its respective energy.
3. Add up each, and assign positive values for bonds breaking, and negative values for bonds forming.
4. Add and stop writing.

Question 4

How to preform the law of Hess

Answer 4

1. Set each equation on top of each other
2. Flip each one until they cancel out to make the final equation.
   - If you double an equation, double the enthalpy
   - if you flip an equation, flip the enthalpy.
3. Add up the final temperatures to get the final answer…