enthalpy

Definition of atomisation

is the enthalpy change due to the formation of 1 mole of an ionic lattice from gaseous ions.

Standard enthalpy change of formation

enthalpy change due to 1 mole of a compound forming from its constituent elements under standard conditions

Standard enthalpy change of atomisation

enthalpy change of forming of 1 mole of gaseous atoms from the element in its standard state under standard conditions. • This is always endothermic (as it is bond breaking).

First ionisation energy And if it’s needs or exothermic

is the enthalpy change

required to remove one electron from each atom in 1 mole of gaseous atoms to form one mole of +1 gaseous ions. • Always endothermic (as energy need to overcome nuclear

attraction).

First electron affinity and weather its eno or exhothermic

is the enthalpy change

when an electron is added to each atom in 1 mole of gaseous atoms to form one mole of –1 gaseous ions. • Always exothermic (as electron attracted towards nucleus).

Why is the second electron affinity endothermic

Second EA is endothermic as electron is repelled by negative

ion.

What is the measurement of ionic bonds

lattice enthalpy

Why is lattice enthalpy always exothermic

Energy is given out when gaseous ions attract to form a lattice.

What does A more exothermic lattice enthalpy value mean

A more exothermic lattice enthalpy value means higher melting and boiling points as more energy is required to overcome the electrostatic interactions.

When do the most exothermic lattice enthalpies arise

When ions are small, because the ions can get closer

When ions have larger charges, as these ions have stronger

electrostatic forces

Standard enthalpy change of hydration

Accompanies one mole of gaseous ions dissolving in water under standard conditions

Explain the trends of sodium halides down the group

• as ionic radius increases

• Attraction between ions decreases

• Less energy released on formation

• Lattice enthalpy is less negative

Enathalpy change of solution

The enthalpy change accompanying one mole of solute dissolving in water under standard conditions

Why are hydration enthalpies always exothermic

Becuase you are forming new bonds between gaseous ions and water molecules

Why is enthalpy change of solution endo or exothermic

• because the lattice breaks to form gaseous ions

• Then the gaseous ions are attracted the the polar water molecules so a bond is formed

List possible sources of in an enthalpy change experiment and explain how they could be reduced

• If not all the solid is transferred from the weighing boat -

  weighing the weighing boat after the solid has been added.

• Thermometer has accuracy of +0.5 °C which is significant for

  such small temperature changes - Use a datalogger and a

  temperature probe or a more accurate thermometer (0.1°C).

• It is difficult to see if the solid has dissolved

• Measuring cylinder has accuracy of +1cm3 which is 3.8% for

  50cm3 - Use a more accurate measuring cylinder