HELP!! AQA AS Chemistry question

The question said :

State the name given to the enthalpy change represented by the following chemical equation..

C(s) + 1/2 O2 -----> CO(g)

The anwser is, standard enthalpy of formation.

I just don't see why or how?

Reply 1

BinyQuan

7

Standard enthalpy of formation goes like enthalpy change when a substance is formed for its element under standard condition 298k 100kpa and we see nothing else except carbon monoxide formed from its element

If it was combustion CO2 + H20 would be formed

(edited 8 years ago)

Reply 2

IBonfire

7

The definition for Enthalpy of formation is:
The standard enthalpy of formation is defined as the change in enthalpy when one mole of a substance in the standard state (1 atm of pressure and 298.15 K) is formed from its pure elements under the same conditions.
(Source: http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Thermodynamics/State_Functions/Enthalpy/Standard_Enthalpy_Of_Formation)

Which means that carbon is a pure element and so is oxygen. 1 mole of carbon monoxide is formed so this is a standard enthalpy of formation (if it occurs under standard state ofc).

Reply 3

kiiten

18

Original post by X_alwayssmiley

The question said :

State the name given to the enthalpy change represented by the following chemical equation..

C(s) + 1/2 O2 -----> CO(g)

The anwser is, standard enthalpy of formation.

I just don't see why or how?

The definition of enthalpy of formation is the energy change when 1 mole of the compound from its constituent elements (in their molar quantities). Look at the equation - notice that CO is formed from C and O2

Reply 4

X_alwayssmiley

OP

1

Original post by kiiten

The definition of enthalpy of formation is the energy change when 1 mole of the compound from its constituent elements (in their molar quantities). Look at the equation - notice that CO is formed from C and O2