Question

If 25.0 mL of a 0.100 M aqueous sodium hydroxide is mixed with 25.0 mL of a 0.100 M aqueous hydrochloric acid in a calorimeter at an initial temperature of 23.0 degrees Celsius, what is the enthalpy change of this reaction if the final temperature reached in the calorimeter is 25.5 degrees Celsius?

NaOH + HCl yields NaCl + H2O

Answer 1

Monitoring the temperature changes of the water, or solution, allows us to find the "heat" by the water, which is the change in enthalpy.

\(\sf enthalpy~change=mass*specific ~heat~ capacity*Change ~in ~temperature\)

Some common simplifications you might need to make is that the density of the final solution is 1 g/mL and that the specific heat capacity of the solution is 4.18 J/\(C^og\) - which is the specific heat capacity of pure water)

First find the mass of the solution using the density and the final volume.

\(\sf density=\dfrac{mass}{volume}\)

Then use the first equation with the change in temperature (difference between final and initial, \(T_f-T_i\); the mass of the solution, and the specific heat capacity.