Question

In a constant-pressure calorimeter, 50.0 mL of 0.330 M Ba(OH)2 was added to 50.0 mL of 0.660 M HCl. The reaction caused the temperature of the solution to rise from 21.85 °C to 26.35 °C. what is ΔH for this reaction (KJ released per mole of H2O produced)? Assume that the total volume is the sum of the individual volumes and that the density and heat capacity are equal to that of water.

Answer 1

moles of acid HCl = 50 x 0.660 / 1000 = 0.033

moles of Ba(OH)2 = 50 x 0.330 / 1000 = 0.0165

2 HCl    + Ba(OH)2 ------------------------> BaCl2 + 2H2O

2               1

0.033      0.0165                                                     0.033

here both are consumed

moles of water fomred = 0.033

total volume = 50 + 50 = 100 mL

mass of solution = volume x density

                          = 100 x 1

                         =100g

dT = 26.35 -21.85= 4.5 oC

Q = 100 x 4.184 x 4.5

Q = 1883 J

ΔH =molar enthalpy of neutralization = - Q / n

                                                    = -1.883 / 0.033

                                                   = - 57.0 kJ / mol