Calculating enthalpy changes Flashcards
What is the equation for enthalpy change of reaction?
ΔrxnH = ΣvΔfH (products) - ΣΔfH (reactants)
What is the enthalpy of fusion for water?
H2O (s) -> H2O (l)
What is the enthalpy of vaporisation for water?
H2O (l) -> H2O (g)
What is the equation for electrical heating?
q = itV
What is the equation linking sublimation, vaporization, fusion
ΔSubH = ΔFusH + ΔvapH
What would you need to calculate ΔSubH at 0 degrees?
ΔfusH and ΔvapH at zero degrees
What is an example of an ionisation equation?
H(g) -> H+ (g) + e-
What is an example of an electron gain equation?
Cl (g) + e- -> Cl- (g)
What is an example of a bond dissociation equation?
HCl (g) -> H (g) + Cl (g)
How would you work out the heat required for the ionisation of a specific amount of metal?
Use the ionisation energies and work out the number of moles from the grams
Use the equation q = n x ΔH
What are mean bond enthalpies?
Bond enthalpies are averages for related compounds
What is the enthalpy of combustion?
Enthalpy change when 1 mole of a substance is combusted to liquid water and gaseous CO2 and N2 under standard conditions
How do you work out the specific enthalpy for combustion?
Specific enthalpy = ( ΔcomH / kJ mol⁻¹ ) / ( Molar mass / gmol⁻¹)
What is an example equation for dissolution of a salt?
NaCl (s) -> Na+(aq) + Cl-(aq)
What is an example equation of lattice enthalpy for dissolution of a salt?
NaCl (s) -> Na+(g) + Cl-(g)
