[lush_xx]

hello all

i am finding it hard to enter the values for this born haber cycle with a given group of values can someone show me how its done please?

after using a youtube tutorial this is what i calculated:

A =737
B = 400
C = 200
D= 200
F = -1765

but i dont know if it is right

please look at the attachment

[Borek]

How is the enthalpy of formation defined? Can you write reaction equation for the formation of MgX₂(s)?

[lush_xx]

How is the enthalpy of formation defined? Can you write reaction equation for the formation of MgX₂(s)?

I am not too certain the image is a practice question i found online, most youtube videos I watched doesnt seem to cover this type of born haber question

[lush_xx]

How is the enthalpy of formation defined? Can you write reaction equation for the formation of MgX₂(s)?

Mg+X₂ = MgX₂ ?

[Borek]

Your reaction equation misses states - add them and compare the reaction you wrote with the reactions D and F. Which one is it?

[lush_xx]

I don't get it, how to I know where to input the values given

[Borek]

Large part of what you did is OK, but not everything.

Which of the processes - D or F - is a formation of the MgX₂(s)? How is the formation defined?

[lush_xx]

I think D would be the formation as it has mgx2(s)

[lush_xx]

Large part of what you did is OK, but not everything.

Which of the processes - D or F - is a formation of the MgX₂(s)? How is the formation defined?

as D is formation perhaps the value  is -450 but I dont know how to calculate the other boxes with just this figure

[Borek]

I will ask for the third time: please quote the definition of the formation enthalpy.

As long as you ignore what you are being asked we won't move forward.

[lush_xx]

I will ask for the third time: please quote the definition of the formation enthalpy.

As long as you ignore what you are being asked we won't move forward.

change of enthalpy where 1 mole of a particular element is formed from their component in their standard form?

[Borek]

in their standard form?

What is the standard form for Mg and for X?

Hint: Mg(s) or Mg²⁺(g)?

[lush_xx]

in their standard form?

What is the standard form for Mg and for X?

Hint: Mg(s) or Mg²⁺(g)?

Mg(s) as it is at the bottom of the cycle

[Borek]

Mg(s) as it is at the bottom of the cycle

No, it is not because it is at "the bottom of the cycle", standard states are defined: https://en.wikipedia.org/wiki/Standard_state

But yes, Mg(s) is the standard state. So, if the Mg(s) is a standard state, and the formation enthalpy is formation from standard state, which process - D or F - is the formation of MgX₂(s)?

Once you assign correctly enthalpy of the formation of MgX₂(s) to one of the processes in the cycle it will be obvious what is left to calculate - and it should be also obvious how to calculate it.

[Aldebaran]

Together with Borek's coaching, the following link may help you: https://www.chemguide.co.uk/physical/energetics/lattice.html