M5 - Enthalpy and Entropy Flashcards
Write an equation, with state symbols, for the enthalpy change of hydration for sodium (1)
Na+(g) + aq 🡪 Na+(aq)
Write an equation to represent the atomisation of bromine (1)
½ Br2(l) 🡪 Br(g)
What is the ‘Standard entropy change of a reaction’, ΔSθ:
The entropy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states
Define ‘ First electron affinity’, ΔEA1Hϑ:
The enthalpy change when one electron is added to each atom in one mole of gaseous atoms, to form one mole of gaseous 1- ions
B
D
Write an equation, with state symbols, for the lattice enthalpy of potassium chloride (1)
K+(g) + Cl-(g) 🡪 KCl(s)
How would the entropy change during the enthalpy of solution of calcium oxide ?
Increase as 1 mole of solid is completely dissolved in water, forming more disordered aqueous ions
Write the equation to calculate entropy change (1)
ΔSθ = ∑Sθ(products) - ∑Sθ(reactants)
Define ‘Second electron affinity’, ΔEA2Hϑ
The enthalpy change when one electron is added to each ion in one mole of gaseous 1- ions, to form one mole of gaseous 2- ions
A
Would freezing water increase or decrease the entropy change?
Decrease, as solids have less disorder than liquids
Write an equation, with state symbols, for the enthalpy of solution of NaCl (1)
NaCl(s) + aq 🡪 Na+(aq) + Cl-(aq)
How would the entropy change when calcium carbonate reacts with hydrochloric acid?
Increase, as 1 mole of gas is formed from 0 moles of gas
How is the temperature for reaction feasibility determined?
Set ΔG to be zero, and rearrange to;
T = ΔH / ΔS
Define ‘Enthalpy change of atomisation’, ΔatHϑ:
The enthalpy change when the one mole of gaseous atoms is formed from its element, under standard conditions
A
What is the Gibbs equation?
ΔG = ΔH – TΔS
ΔG < 0 (-ve) Reaction is feasible
ΔG > 0 (+ve) Reaction is not feasible
When is a reaction feasible/spontaneous in terms of ΔG ?
Only when ΔG is negative in value
Write an equation to represent the second electron affinity of oxygen.
O-(g) + e- 🡪 O2- (g)
Define ‘Standard Enthalpy Change of Solution’, ΔsolHϑ (1)
Enthalpy change that takes place when one mole of compound (solute) is completely dissolved in water under standard conditions (1)
Write an equation to represent the first electron affinity for chlorine (1)
Cl(g) + e- 🡪 Cl-(g)
Define ‘Lattice Enthalpy’, ΔLEH (1)
Enthalpy change when one mole of an ionic compound is formed from its gaseous ions (1)
D
Define ‘Standard Enthalpy Change of Hydration’, ΔhydHϑ (1)
The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqueous ions under standard conditions (1)
What is meat by ‘Entropy’, S?
A measure of the dispersal of energy in a system. The entropy is greater when the system is more disordered. A system becomes energetically more stable when it becomes more disordered
