Gridlocks – can you unlock the grid?
Born-Haber cycle: MgCl2
The Born-Haber cycle can by divided into stages like the ones in the table below. Start by filling in the table
using:
−
Mg (g) + 2Cl (g) MgCl2(s)
2+
Mg(s) + Cl2(g)  MgCl2(s)
standard enthalpy
change(s)
stage
∆H
elements to gaseous atoms
θ
at Mg
st
& 2∆H
Mg(g)  Mg (g) + 2e
2+
−
equation(s)
Mg(s)  Mg(g)
θ
at Cl
Cl2(g)  2Cl(g)
nd
atoms to positive ions
1 + 2 IE of Mg
atoms to negative ions
2 x 1 EA of Cl
gaseous ions to solid lattice
lattice enthalpy (formation)
elements to compound
∆H f MgCl2
−
−
2Cl(g) + 2e  2Cl (g)
st
θ
Gridlock 1
Each row, column and 2 x 2 box contains information about the first four stages listed. Use your problem
solving skills and the answers in the table above to fill in the blank boxes.
stage
standard enthalpy change(s)
∆H
atoms to positive ions
θ
at Mg
& 2∆H
θ
at Cl
gaseous ions to solid
lattice
st
2 x 1 EA of Cl
standard enthalpy change(s)
stage
Gridlocks – can you unlock the grid?
Gridlock 2
Each row, column and 2 x 2 box contains information about each of the last four stages listed.
stage
equations
Mg(s) +Cl2(g) 
MgCl2(s)
atoms to positive ions
−
lattice enthalpy
(formation)
−
2Cl(g) + 2e  2Cl (g)
equations
standard enthalpy change(s)
Gridlock 3
You will need to work out which stages are in this gridlock.
stage
equations
elements to gaseous
atoms
−
Mg (g) + 2Cl (g) 
MgCl2(s)
2+
Mg(s)  Mg(g)
Cl2(g)  2Cl(g)
−
Mg(g)  Mg (g) + 2e
2+
equations
θ
∆H f MgCl2
standard enthalpy change(s)