A pure sample of Substance S is put into an evacuated flask. The flask is then heated steadily and the temperature measured as time passes. The results are graphed below, in the middle (in green). Identical experiments are now run on Substance Y and Substance Z. Substance Y is just like S'except that it has a lower enthalpy of fusion AH. Substance is just like S except that it has a higher enthalpy of vaporization AH,. Select the graphs below, on the left and right, that show the results you expect for these new experiments. temperature (°C) Substance Y (lower AH) added heat (kJ/mol) temperature (°C) Substance S added heat (kJ/mol) temperature (°C) Substance Z (higher ΔΗ.) added heat (kJ/mol)
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.
The steps starting from the origin are-
1) heating of solid
2) fusion
3) heating of liquid
4) evaporation
5) heating of gas
Now, as Y has a higher heat capacity in the gaseous phase, so it's increase in temperature with adding heat will be slow in the gaseous phase. So, step 5 will have a lower slope as compared to S.
So, the graph for Y is the one on the right.
Now, as Z has a lower enthalpy of fusion, so the segment for the step 2 will be shorter than that in the graph for S.
The graph of Z is not the either one that you have given.
Please look for a graph which is exactly like S except for it's segment for step 2 is shorter. That is the lower horizontal segment.
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