Calculate the ph of a buffer solution prepared by mixing 60.0 ml of 1.00 m lactic acid and 25.0 ml of 1.00 m sodium lactate.
(the pka for lactic acid is 3.86. the molar mass for lactic acid is 90.1 g/mol and the molar mass for sodium lactate is 112.1 g/mol.)

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.