But in the answer options:

Question

a) -27.4 kJ
b) -72.8 kJ
c) -78.4 kJ
d) -84.6kJ

I attempted this problem in the other way.When using the q =mcdT,I added the mass of both water and sulfuric acid.

q = (300g +10.65g)(4.184J/g.K)(6.55C)
  = 8513.43 J

Then, I calculated the mole of sulfuric acid ,n = 10.65g/(98.08g/mol) = 0.1086mol

Since the question asks for heat evolved/mole of H2SO4,so 
q sulfuric acid = 8513.43J/(0.1086mol)x 1 mol of H2SO4
                = -78.4 kJ(option c)

Need detailed   explanation.Thank you.

DrBob222 · Answer

That looks good to me. I ignored the H2SO4 when I responded to your question earlier; it appears that is not acceptable.