For the following questions (Q11-Q14), consider the compound NH4Cl, ammonium chloride, having a molar mass of 53.491 g/mol. Nicole weighs out 12.41g of NH4Cl and also 125.0 g of water for her calorimetry experiment. Nicole dissolves her ammonium chloride in the water and finds that the temperature of the water decreases from 23.7°C to 17.3°C. Assume the specific heat capacity of the water, Cs,water, is 4.184 J/(g °C) and that no energy is transferred to the calorimeter (qcal = 0 J) Q11. Find the heat (in J) transferred to the water, qwater, during the process NH4Cl (s) ® NH4Cl (aq). Use the equation qwater = mwater Cs,water ∆T. Q12. Is the dissolving of ammonium chloride an endothermic or exothermic process? Q13. Using your result in Q11, calculate the enthalpy of reaction, ∆Hrxn, in units of kJ/mol. Q14. If the true value for ∆Hrxn is +14.8 kJ/mol, calculate Nicole’s percent error.
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.
For the following questions (Q11-Q14), consider the compound NH4Cl, ammonium chloride, having a molar mass of 53.491 g/mol. Nicole weighs out 12.41g of NH4Cl and also 125.0 g of water for her calorimetry experiment. Nicole dissolves her ammonium chloride in the water and finds that the temperature of the water decreases from 23.7°C to 17.3°C. Assume the specific heat capacity of the water, Cs,water, is 4.184 J/(g °C) and that no energy is transferred to the calorimeter (qcal = 0 J)
Q11. Find the heat (in J) transferred to the water, qwater, during the process NH4Cl (s) ® NH4Cl (aq). Use the equation qwater = mwater Cs,water ∆T.
Q12. Is the dissolving of ammonium chloride an endothermic or exothermic process?
Q13. Using your result in Q11, calculate the enthalpy of reaction, ∆Hrxn, in units of kJ/mol.
Q14. If the true value for ∆Hrxn is +14.8 kJ/mol, calculate Nicole’s percent error.
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