Enthalpy and Energy Changes in Chemical Reactions

A set of flashcards covering important concepts, definitions, and formulas related to enthalpy and energy changes in chemical reactions.

What are the two types of enthalpy changes in chemical reactions?

Exothermic (ΔH negative) and Endothermic (ΔH positive).

What does Hess' Law state?

If a reaction can take place via two different pathways, the total enthalpy change is the same for both routes.

What is the formula used to determine the energy change (q) in a chemical reaction?

q = mcΔT, where m is the mass, c is the specific heat capacity, and ΔT is the temperature change.

Define average bond enthalpy.

The energy required to break one mole of a specific type of bond in a gaseous molecule.

What is activation energy (Ea)?

The minimum energy required for a reaction to occur.

What is the standard enthalpy change of formation (ΔfH)?

The enthalpy change for the formation of one mole of a compound from its elements.

How can you calculate the enthalpy change from average bond enthalpies?

ΔH = Σ(bond enthalpies of reactants) - Σ(bond enthalpies of products).

What is the definition of the enthalpy change of neutralization (ΔneutH)?

The energy change when one mole of water is formed by the neutralization of an acid by an alkali.

What are standard conditions for measuring enthalpy changes?

Temperature = 298 K, Pressure = 100 kPa, Concentration = 1 moldm-3.

What type of reaction occurs when more energy is released in bond forming than is absorbed in bond breaking?

An exothermic reaction.

What type of reaction occurs when more energy is absorbed in bond breaking than is released in bond forming?

An endothermic reaction.

When calculating ∆H, which unit is commonly used?

kJmol-1.

What does the term 'enthalpy profile diagram' represent?

A graphical representation of the energy changes during a chemical reaction, showing the enthalpy of reactants and products.

What is the relationship between temperature change (∆T) and the type of reaction when monitoring reactions?

An increase in temperature indicates an exothermic reaction, while a decrease indicates an endothermic reaction.

How do you calculate the enthalpy change of neutralization from experimental data?

By measuring the temperature change (∆T) when an acid reacts with an alkali and calculating q using q = mc∆T, then finding moles, and finally calculating ∆H.