Chapter 9 Flashcards
What is an enthalpy change?
Is a change in heat energy of a system measured under constant pressure.
What is exothermic reaction?
Is one where the system loses energy.
What is an endothermic reaction?
Is one where the system gains energy.
What is activation energy?
Is the minimum energy required for a reaction to take place.
What is enthalpy change of reaction?
Enthalpy change associates with a stated equation.
What is enthalpy change of formation?
Enthalpy change when 1 mole of a compound is formed from its elements.
What is enthalpy change of combustion?
Enthalpy change when 1 mole of a substance is completely combusted.
What is enthalpy change of neutralisation?
Enthalpy change when 1 mole of water is formed from neutralisation.
What are standard states?
Physical states under standard conditions.
What are standard conditions?
100kpa and a temperature of 298k.
What is the equation for enthalpy change?
Q=MC(delta)T Q- heat energy(J) M- mass (g) C- specific heat capacity (jg-1k-1) (delta)T= temperature change (K)
What is the general method to use Q=MC(delta)T for experiments?
1) Use the equation to calculate energy change
2) Work out the moles of reactants used
3) Divide q by the number of moles of the reactants not used in excess to give (delta)H
4) Add a sign and unit (KJmol-1) — jmol-1 divide by 1000 to get kjmol-1.
What is the average bond enthalpy?
Is the energy required to break 1 mole of a specified type of bond in a gaseous molecule.
What is the equation used to estimate reaction enthalpies?
Sum of bond enthalpy of reactants - Sum of bond enthalpy of products
What is the equation for enthalpy of combustion?
Reactants-products
