Q3) a) The following information is given for water, H2O, at 1atm: boiling point = 100 °C Hvap(100 °C) = 40.7 kJ/mol specific heat liquid = 4.18 J/g°C At a pressure of 1 atm,______ kJ of heat are needed to vaporize a 47.5 g sample of liquid water at its normal boiling point of 100 °C. b)The following information is given for ethanol, C2H5OH, at 1atm: boiling point = 78.4 °C Hvap(78.4 °C) = 38.6 kJ/mol specific heat liquid = 2.46 J/g°C At a pressure of 1 atm, what is H in kJ for the process of condensing a 25.5 g sample of gaseous ethanol at its normal boiling point of 78.4 °C. ________kJ c)The following information is given for n-pentane, C5H12, at 1atm: boiling point = 36.2 °C Hvap(36.2 °C) = 25.8 kJ/mol specific heat liquid = 2.28 J/g°C At a pressure of 1 atm,_______ kJ of heat are needed to vaporize a 31.3 g sample of liquid n-pentane at its normal boiling point of 36.2 °C.
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.
Q3)
a)
The following information is given for water, H2O, at 1atm:
| boiling point = 100 °C | Hvap(100 °C) = 40.7 kJ/mol |
| specific heat liquid = 4.18 J/g°C |
At a pressure of 1 atm,______ kJ of heat are needed to vaporize a 47.5 g sample of liquid water at its normal boiling point of 100 °C.
b)The following information is given for ethanol, C2H5OH, at 1atm:
| boiling point = 78.4 °C | Hvap(78.4 °C) = 38.6 kJ/mol |
| specific heat liquid = 2.46 J/g°C |
At a pressure of 1 atm, what is H in kJ for the process of condensing a 25.5 g sample of gaseous ethanol at its normal boiling point of 78.4 °C.
________kJ
c)The following information is given for n-pentane, C5H12, at 1atm:
| boiling point = 36.2 °C | Hvap(36.2 °C) = 25.8 kJ/mol |
| specific heat liquid = 2.28 J/g°C |
At a pressure of 1 atm,_______ kJ of heat are needed to vaporize a 31.3 g sample of liquid n-pentane at its normal boiling point of 36.2 °C.
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