Enthalpy

What is enthalpy

The SUM of all forms of kinetic and potential energy in a system (Ek + Ep)

Changes in enthalpy occur whenever heat is WHAT in a WHAT

Changes in enthalpy occur whenever heat is RELEASED or ABSORBED in a CHEMICAL CHANGE

Enthalpy change = ∆H (heat) is measured in WHAT

J or KJ

∆rH =

Enthalpy of reaction

∆cH =

Enthalpy combustion

∆rH° =

Standard enthalpy of reaction ( at SATP - 100KPa and 25°C)

“°” symbol is used to denote changes taking place at WHAT conditions

Standard

What is molar enthalpy

It’s the enthalpy change PER MOLE of a substance

Molar enthalpy is also designated ∆H, although we will be using WHAT for our formulas

H

Molar enthalpy is measured in WHAT

J/mol or KJ/mol

Molar enthalpy, in KJ/mol and the number of a substance can be used to calculate the WHAT

Enthalpy change of a phase change

What is the equation

∆H = nH

where:

∆H = Enthalpy change in KJ or J

n = number of moles in mol

H = Molar enthalpy per 1 mol in KJ/mol or J/mol

Exothermic is WHAT

Endothermic is WHAT

Exothermic is NEGATIVE KJ

Endothermic is POSITIVE KJ

What are the 3 ways the the number of moles can come form

1. The BALANCING of COEFFICIENTS in the chemical reaction (no other info given)

2. From n = m/M if MASS is given

3. From n = CV if CONCENTRATION or VOLUM is given