Enthalpy change of atomisation of Iodine

LauraEddy

14

The equation is:
1⁄2 I2(s)  ----> I(g)

Why is 1⁄2 I2 solid and not gaseous?

Reply 1

Ðeggs

22

Because iodine is a solid at room temperature and the enthalpy changes are taken at 298K and 100KPa

Reply 2

LauraEddy

OP

14

Thank you! So, why does it become gaseous after the atomisation has taken place, do the conditions change during the reaction?

Original post by Deggs_14

Because iodine is a solid at room temperature and the enthalpy changes are taken at 298K and 100KPa

Reply 3

Ðeggs

22

Original post by LauraEddy

Thank you! So, why does it become gaseous after the atomisation has taken place, do the conditions change during the reaction?

I believe this is to do with the Maxwell-Boltzman distribution. For a given number of particles in 1/2 I2 (s), some particles will have enough activation energy so the reaction can occur. Enthalpy of atomisation is defined as the amount of energy required for a substance in standard conditions to form one mole of gaseous atoms. As all of the bonds are broken but none are formed, the value is always positive, so energy is required to be inputted into the system, which comes as heat.

Reply 4

LauraEddy

OP

14

Original post by Deggs_14

I believe this is to do with the Maxwell-Boltzman distribution. For a given number of particles in 1/2 I2 (s), some particles will have enough activation energy so the reaction can occur. Enthalpy of atomisation is defined as the amount of energy required for a substance in standard conditions to form one mole of gaseous atoms. As all of the bonds are broken but none are formed, the value is always positive, so energy is required to be inputted into the system, which comes as heat.