Use the following data to answer part A: mixing NaOH(s) into plain water released 1541 J of heat mixing NaOH(s) into HCl(aq) released 3498 J of heat mixing NaOH(aq) into HCl(aq) released 2000 J of heat Show that this data either supports or contradicts Hess’s Law and be clear in your explanation by using chemical equations and numerical calculations. Assume that all three parts use the same amount of NaOH and for the two parts using HCl(aq), the same amount of HCl was used as well. Hint: The sign of your values are important.
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.
Use the following data to answer part A:
- mixing NaOH(s) into plain water released 1541 J of heat
- mixing NaOH(s) into HCl(aq) released 3498 J of heat
- mixing NaOH(aq) into HCl(aq) released 2000 J of heat
Show that this data either supports or contradicts Hess’s Law and be clear in your explanation by using chemical equations and numerical calculations. Assume that all three parts use the same amount of NaOH and for the two parts using HCl(aq), the same amount of HCl was used as well. Hint: The sign of your values are important.
Given :
- mixing NaOH(s) into plain water released 1541 J of heat
- mixing NaOH(s) into HCl(aq) released 3498 J of heat
- mixing NaOH(aq) into HCl(aq) released 2000 J of heat
Mixing of NaOH (s) in water will dissolve the solid into aqueous form as
1) NaOH (s) ------> NaOH (aq) => ΔH = -1541 J ( -ve because heat is being released in the process)
Mixing of NaOH (s) with HCl (aq) will have a neutralisation reaction as NaOH is a strong base and HCl is a strong acid as
2) NaOH (s) + HCl (aq) --------> NaCl (aq) + H2O (l) => ΔH = -3498 J ( -ve because heat is being released in the process)
And Mixing of NaOH (aq) with HCl (aq) will also have a neutralisation reaction as NaOH is a strong base and HCl is a strong acid as
3) NaOH (aq) + HCl (aq) --------> NaCl (aq) + H2O (l) => ΔH = -2000 J ( -ve because heat is being released in the process)
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