Chapter 9 - Enthalpy Flashcards
What is the law of conservation of energy?
Energy cannot be created or destroyed
What is an exothermic enthalpy change
Transfer of energy from the system to the surroundings (negative delta H)
What is an endothermic enthalpy change?
transfer of energy from the surroundings to the system (positive delta H)
What is activation energy?
The energy required to break
What is activation energy?
The minimum energy required to start a reaction by braking bonds
What are standard conditions?
Pressure = 100KPa
Temperature = 298 K
Concentration = 1 mol dm ^-3
What is the standard enthalpy change of a reaction?
The enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation, under standard conditions, with all reactants and products in their standard states.
What is the standard enthalpy change of combustion?
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, with all reactants and products in their standard states
What is the standard enthalpy change of formation?
The enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard states
What is the standard enthalpy change of neutralisation?
The enthalpy chnage that takes place in the reaction of an acid by a base to form one mole of H2O under standard conditions, with all reactants and products in their standard states
How do you convert from degrees Celsius to Kelvin?
Add 273
How do you calculate energy change (Q)?
Q = mcΔT
Why is the experimental value of heat of combustion lower than the actual value of heat of combustion?
-Heat energy is lost to the surroundings
-Incomplete combustion may take place which produces carbon monoxide and carbon instead of carbon dioxide
-There may be evaporation of the alcohol from the wick
-The reaction is likely to not have been carried out under standard coditions
