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Enthalpy Changes for Solids and Solutions

Enthalpy changes of atomisation, lattice and hydration

  • 3 things to know
  • Component 1

Overview

Standard enthalpy change of atomisation, why an enthalpy change of atomisation is always endothermic and lattice formation enthalpy of an ionic compound.

What you need to know

Answer each one before you reveal it.

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Key term

Why is a lattice formation enthalpy always exothermic, and what two properties of the ions decide how exothermic it is?

Key term

Explain why an enthalpy change of atomisation is always endothermic.

Key term

Write the equation that represents the standard enthalpy change of atomisation of chlorine.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define the standard enthalpy change of atomisation.

    Model answer

    It is the enthalpy change when one mole of gaseous atoms is formed from an element in its standard state.

  2. 2

    Explain why an enthalpy change of atomisation is always endothermic.

    Model answer

    Energy has to be supplied to break the bonds or overcome the attractions holding the atoms together in the element.

  3. 3

    Write the equation that represents the standard enthalpy change of atomisation of chlorine.

    Model answer

    ½Cl₂(g) → Cl(g).

  4. 4

    Write the equation that represents the standard enthalpy change of atomisation of sodium.

    Model answer

    Na(s) → Na(g).

  5. 5

    Define the lattice formation enthalpy of an ionic compound.

    Model answer

    It is the enthalpy change when one mole of the ionic solid is formed from its constituent gaseous ions.

  6. 6

    Explain why a lattice formation enthalpy is always exothermic.

    Model answer

    Oppositely charged ions come together from infinite separation and strong electrostatic attractions are formed, which releases energy.

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