Edexcel IAL Chemistry 6.4 Standard enthalpy-change definitions

Identify the named enthalpy quantity, write an equation for exactly one mole of the required species and ensure every element or substance is in its standard state.

Exam points

Select formation equations that produce exactly one mole from elements in standard states.
Define combustion, neutralisation or atomisation through the required one-mole change.
Explain why an element in its standard state has zero standard formation enthalpy.

[Maximum number: 2]

This question is about sodium hydroxide.

State what is meant by standard enthalpy change of neutralisation, $\Delta_{\text {neut }} H^{\ominus}$ .

An answer that makes reference to the following points:

- heat energy released under standard conditions (1)

- (when) 1 mol of water is produced (by the reaction of (1) acid with alkali)

Allow enthalpy change under standard conditions
Allow for standard conditions $1 \mathrm{~atm} / 1(.01) \times 10^{5} \mathrm{~Pa}$
and a stated temperature / $298 \mathrm{~K} / 25^{\circ} \mathrm{C}$
Ignore standard states
Do not award required

(2)

All question bank results loaded

6.4—The definition of standard enthalpy change of: i reaction, ∆rH ii formation, ∆fH iii combustion, ∆cH iv neutralisation question 1