A 100.0-mL sample of 1.0 M NaOH is mixed with 50.0 mL of 1.0 M H2SO4 in a large Styrofoam coffee cup; the cup is fitted with a lid through which a calibrated thermometer passes. The temperature of both solutions before mixing is 22.3 °C. After the NaOH solution is added to the coffee cup and the mixed solutions are stirred with the thermometer, the maximum temperature measured is 31.4 °C. Assume that the density of the mixed solution is 1.00 g/mL, the specific heat of the mixed solutions is 4.18 J/g•°C, and no heat is lost to the surroundings. (a) Write a balanced chemical equation for the reaction that takes place. (b) Is there any unreacted NaOH or H2SO4 remaining after the reaction? (c) Calculate the enthalpy change per mole of H2SO4 in the reaction.
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
A 100.0-mL sample of 1.0 M NaOH is mixed with 50.0 mL of 1.0 M H2SO4 in a large Styrofoam coffee cup; the cup is fitted with a lid through which a calibrated thermometer passes. The temperature of both solutions before mixing is 22.3 °C. After the NaOH solution is added to the coffee cup and the mixed solutions are stirred with the thermometer, the maximum temperature measured is 31.4 °C. Assume that the density of the mixed solution is 1.00 g/mL, the specific heat of the mixed solutions is 4.18 J/g•°C, and no heat is lost to the surroundings.
(a) Write a balanced chemical equation for the reaction that takes place.
(b) Is there any unreacted NaOH or H2SO4 remaining after the reaction?
(c) Calculate the enthalpy change per mole of H2SO4 in the reaction.
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