OBHB - Module 3.2 Flashcards
What is chemical energy?
A form of potential energy stored in chemical bonds.
What is enthalpy?
The heat content stored in a chemical system.
What is delta H short for and how is it calculated?
Enthalpy change: products’ enthalpy - reactants’ enthalpy.
What is the activation energy?
The minimum amount for energy needed to start a reaction
Define average bond enthalpy.
The average enthalpy change that takes place when breaking by homolytic fission 1 mole of a given type of bond in the molecules of a gaseous species.
What are the four standard conditions?
- Pressure of 100kPa
- Temperature of 298K (25 degrees C)
- Substances in their standard state
- Solution have a concentration of 1 mol/dm^3
What is standard state?
The physical and chemical state that you would expect to find a chemical in, under standard conditions.
In the notation for standard conditions, what does the H mean?
Heat energy
In the notation for standard conditions, what does the theta mean?
Standard conditions
In the notation for standard conditions, what does the x mean?
Type of change
Define “standard enthalpy change of reaction“.
The enthalpy change when a reaction occurs in the molar quantities shown in the chemical equation, under standard conditions.
Define “standard enthalpy change of formation“.
The enthalpy change when one mole of a compound is formed from its elements in their standard states, under standard conditions.
Define “standard enthalpy change of combustion“.
The enthalpy change when one mole of a substance is completely burnt in oxygen, under standard conditions.
Define “standard enthalpy change of neutralisation“.
The enthalpy change when acids react with alkalis in aqueous solution to form a salt and one mole of water.
