Question

A 98.2 mL sample of 1.00 M NaOH is mixed with 49.1 mL of 1.00 M H2SO4 in a large Styrofoam coffee cup; the cup is fitted with a lid through which passes a calibrated thermometer. The temperature of each solution before mixing is 21.45 °C. After adding the NaOH solution to the coffee cup and stirring the mixed solutions with the thermometer, the maximum temperature measured is 32.10 °C. Assume that the density of the mixed solutions is 1.00 g/mL, that the specific heat of the mixed solutions is 4.18 J/(g·°C), and that no heat is lost to the surroundings. Write a balanced chemical equation for the reaction that takes place in the Styrofoam cup. Remember to include phases in the balanced chemical equation. Calculate the enthalpy change per mole of H2SO4 in the reaction.

Answer 1

2NaOH (aq) + H2SO4(aq)--------------> Na2SO4(aq) + 2H2O(l)

no of moles of NaOH = molarity * volume in L

                                   = 1*0.0982   = 0.0982 moles

no of moles of H2So4 = molarity * volume in L

                                    = 1*0.0491    = 0.0491moles

total volume of solution   = 98.2 + 49.1   = 147.3ml

mass of solution               = volume of solution * density of solution

                                           = 147.3*1   = 147.3g

q    = mcT

      = 147.3*4.18*(32.1-21.45)   = 6557.35J     = 6.55735KJ

     = 6.55735Kj/0.0982mole    = 66.78KJ/mole