AP CHEM Unit 4 Review Days 3-4

Front

What is the formula for calculating the change in enthalpy (ΔH) for a reaction?

Back

ΔH = Σ (Bond Energies of Reactants) - Σ (Bond Energies of Products)

Front

What does a negative ΔH value indicate about a reaction?

Back

A negative ΔH value indicates that the reaction is exothermic, meaning it releases heat.

Front

Define a formation reaction in chemistry.

Back

A formation reaction is a reaction that forms one mole of a compound from its elements in their standard states.

Front

What is the standard enthalpy of formation (ΔH°f)?

Back

The standard enthalpy of formation (ΔH°f) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states.

Front

How do you determine if a reaction is a standard formation reaction?

Back

A reaction is a standard formation reaction if it produces one mole of a compound from its elements in their standard states.

Front

What is the significance of bond energies in calculating ΔH°rxn?

Back

Bond energies are used to estimate the change in enthalpy (ΔH°rxn) by calculating the energy required to break bonds in reactants and the energy released when forming bonds in products.

Front

What is the enthalpy change for the reaction A → B if it is given as -100 kJ?

Back

The enthalpy change for the reaction A → B is -100 kJ, indicating that the reaction is exothermic.

Front

What is the relationship between bond strength and bond energy?

Back

Bond strength is directly related to bond energy; stronger bonds have higher bond energies.

Front

What is the enthalpy change (ΔH) for a reaction that absorbs heat?

Back

The enthalpy change (ΔH) for a reaction that absorbs heat is positive, indicating that the reaction is endothermic.

Front

What is the standard state of an element?

Back

The standard state of an element is its most stable form at 1 atm pressure and a specified temperature, usually 25°C (298 K).