Question

In a constant-pressure calorimeter, 65.0 mL of 0.340 M Ba(OH)2 was added to 65.0 mL of 0.680 M HCl. The reaction caused the temperature of the solution to rise from 24.38 °C to 29.01 °C. If the solution has the same density and specific heat as water (1.00 g/mL and 4.184 J/g·°C, respectively), what is ΔH for this reaction (per mole of H2O produced)? Assume that the total volume is the sum of the individual volumes.

Answer 1

volume of mixed solution = 65ml(Ba(OH)2+ 65 ml (HCl)= 130ml

mass of the solution = volume* density =130 ml*1g/ml= 130 gm

enthalpy change= mass of solution* specific heat* temperaure difference= 130*4.184*(29.01-24.38)=2518 joules

moles of Ba(OH)2 = molarity* volume in L = 0.34*65/1000 =0.0221, moles of HCl = 0.68*65/1000 = 0.0442

The reaction between Ba(OH)2 and HCl is Ba(OH)2+2HCl ------->BaCl2+2H2O

1 mole of Ba(OH)2 reacts with 2 moles of HCl to produce 2moles of water

0.0221 moles of Ba(OH)2 reacts wity 0.0442 moles of HCl to produce 0.0442 moles of water

hence enthalpy change per mole of water= 2518/0.0442=56968 J/mole= 56.968 Kj/mole