Respuesta :

There's a simple formula for this. This formula is:

(n)*(delta Hrxn) = (qrxn)

n= moles
delta Hrxn = molar heat 
q = heat

You just have to simply plug in the values
qrxn = (2.8 mol)*(25.7 kJ/mol)
qrxn=71.96 kJ