enthalpy/ energy reactivity 1.1, 1.2, 1.3 Flashcards
exothermic
Describes a reaction in which energy is transferred to the surroundings.
eg. freezing, condensation, deposition, neutralization, combustion
endothermic
Describes a reaction in which energy is transferred from the surroundings. eg. evaporation, melting, sublimation, photosynthesis, thermal decomposition
what results in an increase in temperature during exothermic reactions
during exothermic reactions there is a release in energy as heat, the water molecules surrounding the site of reaction increases kinetic energy this results in an increase in temperature
explain how endothermic reactions results in lowered temperatures
The endothermic process of the evaporation of alcohol absorbs energy from the surroundings resulting in a decrease in temperature of the surroundings.
chemical potential energy
Energy stored in the chemical bonds between particles
describe energy diagram for endothermic reactions
reactants are lower in energy, they then absobr energy and products are found higher up in diagram
describe energy diagram for exothermic reactions
reactants are higher up in duagram, energy is released and products are then found more energtically stable and lower in the diagram
enthalpy
Measurement of heat energy within a system. It is symbolised in expressions by H.
Enthalpy is the amount of heat energy contained in a substance
enthalpy exothermic reactions
negative enthalpy change
enthalpy endothermic reactions
positive enthalpy change
standar enthalpy chnage
The heat energy transferred within a reaction under standard conditions with all substances present in their standard states.
only 1 product, only 1 mol
units of enthalpy
Kj molˆ-1
calorimetry
technique used to measure the heat transfer during a physical or chemical process
Q= mc delta T
Q= thermal energy in joules
m= mass of psecies you are measuring temperture change of
T= change in temperature
delta H= -Q/n
delta H= change in enthalpy
Q= thermal energy
n= number of moles of an identified reactant or product in the chemical reaction
stability of products in exo and endo
exothermic reactions have more stable products because they are in lower energy levels
while endothermic reactions have less stable products because they are in higher energy levels than reactants
bond enthalpy
The energy required to break one mole of chemical bonds in the gaseous state.
bond making and breaking vs exo and endo reactions
bond making= exothermic
bond breaking= endothermic
why are bond enthalpies averages
because the energy required to break a specific type of bond (like C-H) varies depending on the surrounding molecular environment, making a single, exact value impractical.
hess law
Law that states that the total enthalpy change in a chemical reaction is independent of the route by which the chemical reaction takes place, as long as the initial and final conditions are the same.
activation energy
energy recquired to break bonds
enthalpy change
difference between the energy taken in to break bonds and energy given out to make bonds
in a diagram what represents the activation energy
the change that goes from the reactants to the top of the peak while energy gained by reaction enthalpy change is only from reactants to products
what is the spectrochemical series
degree to which ligand causes splitting of the d orbitals
I-<Br-<S2-<Cl-<F-<OH-<H2O<SCN-<NH3<CN-
