(U2) Energetics Flashcards
What are endothermic reactions?
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants
What are exothermic reactions?
A reaction in which the enthalpy of the products is less than the enthalpy of the reactants
What are the standard conditions in chemistry?
298K and 100kPa
What is standard enthalpy change?
Change in heat energy at constant pressure, measured at standard conditions
What is the standard enthalpy of combustion? (2)
- The enthalpy change when one mole of a substance is completely burnt in oxygen
- under standard conditions
What is the standard enthalpy of formation? (2)
- The enthalpy change when one mole of a compound is formed from its elements
- under standard conditions
What is the standard enthalpy of neutralisation? (2)
- The enthalpy change when one mole of water is produced in a neutralisation reaction
- under standard conditions
State the law for the conservation of energy (2)
- Energy cannot be created or destroyed
- but it can change from one form to another
What is Hess’s Law? (2)
+ state it’s equation
- The enthalpy change for a reaction is independent of the route taken,
- provided the initial and final conditions are the same
- ΔH1 = ΔH3 - ΔH2
What is average bond enthalpy? (2)
- The energy required to break one mole of a given bond
- averaged over many compounds
What is the formula for the measurement of energy change in water?
q = m x c x ΔT
M = mass of solution
C = specific heat capacity of water (4.2)
ΔT = change in temperature
In simple terms, how do you calculate enthalpy of formation?
Energy involved in bond breaking - energy involved in bond making
(reactants - products)
In simple terms, how do you calculate enthalpy change?
Energy involved in bond making - energy involved in bond breaking
(Products - reactants)
