Enthalpy changes of neutralisation for strong and weak acids Flashcards Preview

Topic 12.2 (Acid-base titrations) > Enthalpy changes of neutralisation for strong and weak acids > Flashcards

Flashcards in Enthalpy changes of neutralisation for strong and weak acids Deck (7)
Loading flashcards...
1

the standard enthalpy change of neutralisation is

the enthalpy change when one mole of water is produced by the neutralisation of an acid with an alkali when measured at 100kPa and a specified temperature, usually 298K

2

the standard enthalpy change of neutralisation of a strong acid with a strong base will always have

a similar value of around -57.6 kJ mol-1
note that this is exothermic

3

the general equation for the reaction of a weak acid, HA, with a strong base such as soium hydroxide is

HA(aq) + OH-(aq) → A-(aq) + H2O(l)

the majority of the HA molecules are undissociated in this reaction
this means more energy could be required to dissociate these molecules, which is why the ∆neutH for weak acids against a strong base is less than a strong acid with a strong base because less heat energy is given out, instead used to dissociate more acid molecules.

4

dissociation is an ................. process

endothermic (+∆H)

5

hydration is an ................. process

exothermic (-∆H)

6

when acid molecules dissociate in the endothermic process, the ions formed are then ..........................

hydrated by the H2O molecules present in the aqueous solution,so heat energy is released as hydration is an exothermic process

7

two equations used to represent the dissociation of a weak acid, HA, and the subsequent hydration of the ions are:

HA(aq) → H+(g) + A-(g) ∆H = +xkJ mol-1
DISSOCIATION (endothermic)
H+(g) + A-(g) → H+(aq) + A-(aq) ∆H = -ykJ mol-1
HYDRATION (exothermic)

If the magnitude of x is greater than y, then the overall heat energy change will be endothermic