Chapter 9 Enthalpy Flashcards
What is enthalpy?
A measurement of the heat energy in a chemical system
What does the law of conservation of energy state?
Energy can neither be created nor destroyed
What is the energy transfer in an exothermic reaction?
From the system to the surrroudings
What is the energy transfer in an endothermic reaction?
From the surroundings to the system
What is activation energy?
The minimum energy required for a reaction to take place
What are standard conditions?
100kPa pressure
298k Temperautre
What is standard enthalpy change of reaction?
The enthalpy change when the reaction occurs in the molar quantites shown in the chemical equation, under standard conditions
What is standard enthalpy change of formation?
The enthalpy change when 1 mole of a compound is formed from its elements in their standard sates
What is standard enthalpy change of combustion?
The enthalpy change when 1 mole of a substance is completely burned in oxygen
What is standard enthalpy change of neutralisation?
The enthalpy change when an acid and an alkali react together under standard conditions, to form 1 mole of water
What is specific heat capacity?
The energy required to raise the temperature of 1g of a substance by 1K
What is water’s specific heat capacity?
4.18 J/g/K
What is the equation for energy change (Q)?
Q = mc(Delta)T
m = Mass
c = specific heat capacity
Delta T = Change in temp
What are some possilbe reasons why the experimental value of enthalpy change is not completely accurate?
- heat lost to the surroundings
- Incomplete combustion of X
- Evaporation of X from the wick
- Non-standard conditions
What is average bond enthalpy?
The energy required to break one mole of a specified type of bond in a gaseous molecule
