ENTHALPY Flashcards
What is an exothermic reaction?
A reaction where energy, heat energy is transferred from the reaction system to the surroundings; the ΔH is negative
What is an endothermic reaction?
A reaction where heat energy is transferred from the surroundings to the reaction system; the ΔH is positive
What are the system and the surrroundings?
The system includes the reactants, products and any solvents involved in the reaction
The surroundings is the apparatus involved and the laboratory, and even the universe
What are the standard conditions?
Standard pressure - 100 kilopascals
Standard temperature - 298K
Standard concentration (for solutions) - 1 mol dm^-3
Standard state - whatever the substance would be in at the standard conditions
Standard conditions is referred to by a circle with a line through
What is the standard enthalpy change of reaction? (remember exactly)
ΔHr⦵ - The enthalpy change when molar quantities, according to the stated equation react under standard conditons
What is the standard enthalpy change of combustion? (remember exactly)
ΔHc⦵ - The enthalpy change for 1 mol of fuel burnt in plentiful oxygen supply under standard conditions. As standard conditions aren’t possible (you’re heating something, the temperature would rise (this doesn’t need to be included in the definition)) the value is adjusted
What is the standard enthalpy change of formation? (remember exactly)
The enthalpy change when 1 mol of compound is formed from its elements in their standard states under standard conditions
What is the standard enthalpy change of neutralisation?
The enthalpy change that accompanies the reaction of 1 mol of H+ ions with 1 mol of OH- ions, to produce 1 mol of water, under standard conditions; all reactants in standard states
