Question

When 100 mL of Ba(NO3)2 solution at 25 degrees Celsius is mixed with 100 mL solution CaSO4 solution at 25 degrees Celsius in calorimeter, the white solid BaSO4 forms and the temperature of the mixture increases to 28.1 degrees Celsius. Assuming that the calorimeter absorbs only a negligible quantity of heat and the specific heat capacity of the solution is 4.184 J/g.degrees Celsius, and that the density of the final solution is 1.0 g/mL, calculate the enthalpy change of this reaction.

Answer 1

Since the molar irises of the solutions are not given a molar enthalpy can not be calculated. An enthalpy change for the described system can be computed as, since the system is open to the air, q for the reaction equals the enthalpy change and q = mass x specific heat x temperature change. Note that total volume equals 200 mL, so we have:

200 mL x 1.0g/mL x4.184J/g-deg C x (28.1-25). Quantity of heat liberated is thus 2600 J. Note that the chemical reaction is exothermic, as it releases heat to the water and thus has a negative sign.