You mix 45 ml of .20M HCl with 45 ml of .20M KOH in a calorimeter. The temperature of both reactions before mixing is 21.5oC. The temperature rises for the mixture to 22.7oC after mixing. What is the enthalpy change per mole of water produced?

Answer 1

KOH + HCl ==>H2O + KCl

mols HCl = M x L = ?
mols KOH = M x L = ?
mols HCl = mols KOH so the reaction is exactly neutralized and mols H2O prduced is 0.009.

q rxn = mass solution x specific heat solution x delta T
The problem doesn't say what the density is; I assume we are to assume it is 1.00 g/mL. There are 90 mL when mixed so g H2O is 90 grams.
dq = 90 x 4.184 x delta T = approximately 450 but you need a more accurate answer. So
q rxn = 450 J and that is for 0.009
delta H/mol = q/mol = approx 450/0.009 = ? and it is exothermic so the sign of delta H is negative. Most change this to delta H = -??? kJ/mol.