anactualmess
Badges: 10
Rep:
?
#1
Report Thread starter 2 years ago
#1
Would CH4(g) -----> C(g) + 4H(g) or H2 (g) ------> 2H (g) be an example of atomisation or not as more than one mole of gaseous atoms are produced in each case?
0
reply
username3249896
Badges: 12
Rep:
?
#2
Report 2 years ago
#2
https://en.wikipedia.org/wiki/Enthalpy_of_atomization
"Enthalpy of atomization is the amount of enthalpy change when a compound's bonds are broken and the component atoms are reduced to individual atoms.
Enthalpy of atomization is denoted by the symbol ΔHa. The enthalpy change of atomization of gaseous H2O is, for example, the sum of the HO–H and H–O bond dissociation enthalpies.
The enthalpy of atomization of an elemental solid is exactly the same as the enthalpy of sublimation for any elemental solid that becomes a monatomic gas upon evaporation.
When a diatomic element is converted to gaseous atoms, only half a mole of molecules will be needed, as the standard enthalpy change is based purely on the production of one mole of gaseous atoms. When the atoms in the molecule are different isotopes of the same element the calculation becomes non-trivial."

Enthalpy change of atomisation of an element is defined as the enthalpy change which accompanies the formation of one mole of gaseous atoms from its element in its standard state
Enthalpy of atomization of a compound is the amount of enthalpy change when the compound's bonds are broken and the component atoms are reduced to individual atoms.


so
CH4(g) -----> C(g) + 4H(g) yes
H2 (g) ------> 2H (g) no
1/2 H2(g) -> H (g) yes
0
reply
anactualmess
Badges: 10
Rep:
?
#3
Report Thread starter 2 years ago
#3
(Original post by BobbJo)
https://en.wikipedia.org/wiki/Enthalpy_of_atomization
"Enthalpy of atomization is the amount of enthalpy change when a compound's bonds are broken and the component atoms are reduced to individual atoms.
Enthalpy of atomization is denoted by the symbol ΔHa. The enthalpy change of atomization of gaseous H2O is, for example, the sum of the HO–H and H–O bond dissociation enthalpies.
The enthalpy of atomization of an elemental solid is exactly the same as the enthalpy of sublimation for any elemental solid that becomes a monatomic gas upon evaporation.
When a diatomic element is converted to gaseous atoms, only half a mole of molecules will be needed, as the standard enthalpy change is based purely on the production of one mole of gaseous atoms. When the atoms in the molecule are different isotopes of the same element the calculation becomes non-trivial."

Enthalpy change of atomisation of an element is defined as the enthalpy change which accompanies the formation of one mole of gaseous atoms from its element in its standard state
Enthalpy of atomization of a compound is the amount of enthalpy change when the compound's bonds are broken and the component atoms are reduced to individual atoms.


so
CH4(g) -----> C(g) + 4H(g) yes
H2 (g) ------> 2H (g) no
1/2 H2(g) -> H (g) yes
Thank you, I understand why H2(g) ----> 2H(g) isn't an example of atomisation, but I still don't really understand how CH4 (g) ----> C(g) + 4H(g) is an example of atomisation as 4 moles of H(g) are being produced?
0
reply
username3249896
Badges: 12
Rep:
?
#4
Report 2 years ago
#4
(Original post by anactualmess)
Thank you, I understand why H2(g) ----> 2H(g) isn't an example of atomisation, but I still don't really understand how CH4 (g) ----> C(g) + 4H(g) is an example of atomisation as 4 moles of H(g) are being produced?
"Enthalpy of atomization is the amount of enthalpy change when a compound's bonds are broken and the component atoms are reduced to individual atoms.
Enthalpy of atomization is denoted by the symbol ΔHa. The enthalpy change of atomization of gaseous H2O is, for example, the sum of the HO–H and H–O bond dissociation enthalpies.
The enthalpy of atomization of an elemental solid is exactly the same as the enthalpy of sublimation for any elemental solid that becomes a monatomic gas upon evaporation.
When a diatomic element is converted to gaseous atoms, only half a mole of molecules will be needed, as the standard enthalpy change is based purely on the production of one mole of gaseous atoms. When the atoms in the molecule are different isotopes of the same element the calculation becomes non-trivial."
Particularly, look at
"Enthalpy of atomization is the amount of enthalpy change when a compound's bonds are broken and the component atoms are reduced to individual atoms.

Enthalpy of atomization is denoted by the symbol ΔHa. The enthalpy change of atomization of gaseous H2O is, for example, the sum of the HO–H and H–O bond dissociation enthalpies."

It is because all bonds in 1 mole of CH4 are broken to form consitituent (individual) atoms
0
reply
anactualmess
Badges: 10
Rep:
?
#5
Report Thread starter 2 years ago
#5
(Original post by BobbJo)
"Enthalpy of atomization is the amount of enthalpy change when a compound's bonds are broken and the component atoms are reduced to individual atoms.
Enthalpy of atomization is denoted by the symbol ΔHa. The enthalpy change of atomization of gaseous H2O is, for example, the sum of the HO–H and H–O bond dissociation enthalpies.
The enthalpy of atomization of an elemental solid is exactly the same as the enthalpy of sublimation for any elemental solid that becomes a monatomic gas upon evaporation.
When a diatomic element is converted to gaseous atoms, only half a mole of molecules will be needed, as the standard enthalpy change is based purely on the production of one mole of gaseous atoms. When the atoms in the molecule are different isotopes of the same element the calculation becomes non-trivial."
Particularly, look at
"Enthalpy of atomization is the amount of enthalpy change when a compound's bonds are broken and the component atoms are reduced to individual atoms.

Enthalpy of atomization is denoted by the symbol ΔHa. The enthalpy change of atomization of gaseous H2O is, for example, the sum of the HO–H and H–O bond dissociation enthalpies."

It is because all bonds in 1 mole of CH4 are broken to form consitituent (individual) atoms
But more than 1 mole of gas is produced
1
reply
username3249896
Badges: 12
Rep:
?
#6
Report 2 years ago
#6
(Original post by anactualmess)
But more than 1 mole of gas is produced
There are different definitions to be considered:
1. The enthalpy change of atomisation for an element is the enthalpy change when 1 mole of gaseous atoms are formed from the element in its standard state, under standard conditions e.g 1/2H2(g) -> H(g)
2. The enthalpy change of atomisation for a compound is the enthalpy change when 1 mole of the compound in its standard state is reduced to its constituent gaseous atoms, under standard conditions. e.g CH4(g) -> C + 4H

The enthalpy change of atomisation for an element is different to that of the enthalpy change of atomisation for a compound.
0
reply
anactualmess
Badges: 10
Rep:
?
#7
Report Thread starter 2 years ago
#7
(Original post by BobbJo)
There are different definitions to be considered:
1. The enthalpy change of atomisation for an element is the enthalpy change when 1 mole of gaseous atoms are formed from the element in its standard state, under standard conditions e.g 1/2H2(g) -> H(g)
2. The enthalpy change of atomisation for a compound is the enthalpy change when 1 mole of the compound in its standard state is reduced to its constituent gaseous atoms, under standard conditions. e.g CH4(g) -> C + 4H

The enthalpy change of atomisation for an element is different to that of the enthalpy change of atomisation for a compound.
Ah okay thank u so much
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

If you haven't confirmed your firm and insurance choices yet, why is that?

I don't want to decide until I've received all my offers (132)
35.29%
I am waiting until the deadline in case anything in my life changes (49)
13.1%
I am waiting until the deadline in case something in the world changes (ie. pandemic-related) (22)
5.88%
I am waiting until I can see the unis in person (37)
9.89%
I still have more questions before I made my decision (49)
13.1%
No reason, just haven't entered it yet (44)
11.76%
Something else (let us know in the thread!) (41)
10.96%

Watched Threads

View All