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Flashcards in Lattice Energy Deck (8)
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1

Define: lattice energy

The enthalpy change when one mole of an ionic solid is formed from its isolated gaseous ions

2

Explain the effect of ionic charge and ionic radius on the magnitude of lattice energy

Greater ionic charge and smaller ionic radius means higher charge density. Higher charge density means the ion attracts the other ion more strongly so lattice energy is more exothermic (greater magnitude)

3

Define: 1st electron affinity

The enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous -1 ions under standard conditions

4

Explain why the second electron affinity is endothermic

Energy is needed to overcome the repulsion between the electron and anion

5

Define: enthalpy change of solution

The energy change when one mole of an ionic solid dissolves in excess water to form an infinitely dilute solution.

Exothermic: soluble; endothermic: insoluble

SOLution for SOLid

6

Define: enthalpy of hydration

The energy change when one mole of gaseous ions dissolves in excess water to form an infinitely dilute solution

Always exothermic as ions form ion-dipole bonds with H2O

7

Describe and explain the trend in solubility of Group 2 hydroxides down the group

Solubilities increase down the group (HYdroxides go HIgher)

Cation charge density decreases so ions separate more easily

8

Describe and explain the trend in solubility of Group 2 sulfates down the group

Solubility decreases

H(hyd) of cation decreases due to decreases charge density

H(latt) of sulfate decreases but to a lesser extent as sulfate ion, which is larger and so contributes more to H(latt), remains unchanged.

H(sol) = H(hyd) - H(latt) becomes more negative down the group so less soluble