[kpfov]

I tried to solve this problem.. but I am not getting right answer....

can some one please help me with this problem. lattice energy of magnesium sulfide

Mg(s)- >Mg(g)--------------------------------- delta H = 148kj/mol
Mg(g) ->Mg 2+ (g) + 2 electron -------------delta H= 2186kj/mol
S8(s) -> 8S (g)--------------------------------delta H= 2232kj/mol
S(g)+ 2 electrong ->S2-(g) ------------------delta H= -450 kj/mol
8Mg(s) +S8(s) ->8MgS(s)--------------------delta H= -2744

Mg2+(g) +S2- (g)-> MgS(s)------------------------delta H = ??

this is what I did

delta H of lattice energy = Delta H of formation - delta H1 - delta H2 - delta H3 - delta H4
which is : -2744-148-2186-2232- -450 =-6860 kj/mol

However my answer is wrong.... because this is multiple choice and non of options have my answer...

here is the multiple choices

A: -3406
B: -2720
C: 2720
D: 2506

PLEASE HELP ME.. I really need help with this...
if you can not understand the problem, I will send the original version in PDF file.

for any further question please email me : jwkx@hotmail.com

Thank you

[plu]

Be careful of your reactant ratios!  8 moles of sulfur is not the same as 1 mole of sulfur!