chapter 5 Flashcards
what is heat?
a form of energy that flows from something at a higher temperature to do something at a lower temperature
what is temperature?
a measure of the average kinetic energy of particles
what is initial energy?
total amount of energy in a sample of a substance
what is a system?
chemical reaction
what is a surrounding?
everything else in the universe
what is an exothermic reaction?
heat energy is transferred from a system to the surrounding (surroundings get hotter)
what is an endothermic reaction?
a system takes in heat energy from the surroundings (the surroundings get cooler)
what is enthalpy change?
the heat energy exchanged with the surroundings at constant pressure
what is stability?
relative energies of a reactant and products in a chemical reaction
what is conserved in chemical reactions?
total energy
what are the units of enthalpy change?
kJ mol-1
what is specific heat capacity
the energy required to raise the temperature of 1Kg of substance by 1K
what is the equation to calculate amount of heat given out?
q = mcΔT
what does infinite dilution mean?
and further dilution of the solution produces no further enthalpy change
what is hess’s law?
the enthalpy change accompanying a chemical reaction is independent of the pathway between initial and final states
what is standard enthalpy change of formation?
the enthalpy change when one mole of a substance is formed from its elements in their standard states under standard conditions
what is the enthalpy change of a reaction?
The enthalpy change for a reaction that is carried out in a series of steps is equal to the sum of the enthalpy changes for the individual steps
what is bond enthalpy?
enthalpy change when one mole of covalent bonds, in a gaseous molecule, is broken under standard conditions
when are bond enthalpies used
reactions occurring in the gaseous states
what is average bond enthalpy?
energy needed to break one mol of a bond in a gaseous molecule averaged over similar compounds
