Energetics Flashcards
Define Enthalpy change
The amount of heat energy taken in or given out during any change in a system provided the pressure is constant
Describe the enthalpy change in an exothermic reaction (2)
Energy is transferred from the system(chemicals) to the surroundings
The products also have less energy than the reactants
Is the Change in energy positive or negative in an Exothermic reaction
Negative
Give 2 examples of common oxidation exothermic processes
Combustion of fules
Oxidation of carbohydrates such as glucose in respiration
What happens if there is an enthalpy change (2)
Energy is transferred between the system and the surroundings
The system is the chemicals and the surroundings is everything outside the chemicals
Describe the enthalpy change in an endothermic reaction (2)
Energy is transferred from the surroundings to the system
Requires an input of heat energy
What is an example of an endothermic reaction (3)
The thermal decomposition of calcium carbonate
The products have more energy than the reactants
Enthalpy change is positive
What is the standard enthalpy change of formation
The enthalpy change when 1 mole of the compound is formed from its elements under standard conditions (298K and 100kpa) all reactants and products being taken in their standard states
What is the standard enthalpy change of combustion
The enthalpy change that occurs when one mole of a substance is completely combusted in oxygen under standard conditions all reactants and products being in their standard stages
What are the 4 standard conditions
100kPa
298K
Solutions at 1moldm^3
All substances should have their normal state at 298
What does incomplete combustion lead to
Soot( carbon)
Carbon monoxide
Water
It will be less exothermic than complete combustion
