Chapter 9 Enthalpy
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What is activation energy
Ea is the minimum energy required for a reaction to take place.
What are the standard conditions
100 kPa (very close to 1 atm pressure) - 298 K (25 °C) - 1 mol dm-3 – relevant for solutions only - Standard state – the physical state of a substance under standard conditions
What is the Standard enthalpy change of reaction (∆rHθ)
(∆rHθ) is the enthalpy change associated with a stated equation in the molar quantities shown in the chemical equation under standard conditions
What is the Standard enthalpy change of reaction (∆rHθ)
(∆rHθ) is the enthalpy change associated with a stated equation in the molar quantities shown in the chemical equation under standard conditions
What is Standard enthalpy change of formation (∆fHθ)
(∆fHθ) is the enthalpy change associated with the formation of 1 mole of a compound from its elements under standard conditions
What is the standard enthalpy of combustion (∆cHθ)
(∆cHθ) is the enthalpy change associated with the complete combustion of 1 mole of a substance under standard conditions
What is the Standard enthalpy change of neutralisation (∆neutHθ)
(∆neutHθ) is the enthalpy change associated with the formation of 1 mole of water from a neutralisation reaction between an acid and a base, under standard conditions.
What is the (∆neutHθ) for the reaction between a strong acid and a strong base
-57 kJ mol-1
What is the equation for heat energy (q) transferred to the surroundings and what are the units
q = m c ∆T • Mass - g • ∆T - Kelvin • Heat Energy - J
How do you convert from °C to K
add 273
When conduction an experiment (spirit Burner) to find the standard enthalpy of combustion, why is the experimental value less exothermic
Heat loss to the surroundings (beaker and air surrounding the flame) * Incomplete combustion of the fuel * Evaporation of fuel * Not performed under standard conditions
What is average bond enthalpy
The energy required to break one mole of a specified type of bond in a gaseous molecule
What is the unit for average bond enthalpy
kJ mol-1
How do you calculate enthalpy changes from average bond enthalpies
ΔrH = Σ(bond enthalpies in reactants) – Σ(bond enthalpies in products)
What is Hess’ law
If a reaction can take place by two routes, and the starting and finishing conditions are the same, the total enthalpy change is the same for each route