Aquantity of 85.0 ml of 0.900 m hcl is mixed with 85.0 ml of 0.900 m koh in a constant-pressure calorimeter that has a heat capacity of 325 j/°c. if the initial temperatures of both solutions are the same at 18.24°c, what is the final temperature of the mixed solution?

There is a 1:1 neutralization reaction,  so, number of moles:

0.085 l * 0.900 mol/ L = 0.0765 mol HCL

The heat produced:  0.0765 mol * -56.2 kJ/mol = -4.229 kJ (this is the heat of neutralization)

Change in temperature:    The mass to use in the equation Q=cmT.  

4229 J / (4.186 J/gC*170 g) = 6.042 C

Add to the initial temperature:

18.24 + 6.042 = 24.29 C°