C4. Energetics Flashcards
What is ΔHdissѳ?
Bond dissociation enthalpy ; Enthalpy change when 1 mole of bonds of the same type are broken in gaseous molecular standard conditions
What are standard conditions?
298K (25c) , 100KPa, 1moldm3 (for concentrations)
Why do we use mean bond enthalpies?
Each time bonds break the environment of remaining bonds change as does the energy required to break the next successive bond
What is the formula for ΔHrѳ?
Σbonds broken – Σbonds formed
How does energy correlate to bond formation and destruction?
Bond breaking – energy required +ΔH
Bond forming – energy released –ΔH
What is ΔHrѳ?
Standard enthalpy change of reaction ; Enthalpy change which occurs when equation quantities of substances react under standard conditions, with everything in standard state
What is temperature?
Average kinetic energy , independent to number of particles present
What is heat?
Total energy give by all particles in a substance , dependant on number of particles present
What is ΔHѳ?
Standard enthalpy change; amount of heat energy taken in or given out during any change in the system , under standard conditions
What is the definition of exothermic?
Energy released to surroundings, products have less energy; ΔH is -ve
What is the definition of endothermic?
Energy is absorbed from the surroundings; products have more energy; ΔH is +ve
What is calorimetry?
Measuring the ΔH of a reaction
What is the equation for calculating heat transferred?
q = mcΔT ; Heat energy(J) = Mass(G) x Specific heat capacity(JgK) x Change in temperature(K)
When is the ΔH present in calorimetry graphs?
4th minute HCl is added so no result, from 5th minute the values are recorded
What is ΔHcᶱ?
Standard enthalpy of combustion; Enthalpy change when 1 mole of a substance burns completely in oxygen under standard conditions
