If neutralization occurs between different volumes of HCl (hydrochloric acid) and a fixed volume and concentration of NaOH (sodium hydroxide), the graph of temperature against volume of HCl will generally show an initial increase in temperature followed by a decrease.
Initially, when the HCl and NaOH are mixed, an exothermic neutralization reaction takes place. This reaction releases heat energy as the acid and base react to form water and a salt. The heat released increases the temperature of the solution, resulting in an initial rise in temperature.
However, as more HCl is added to the system, the reaction reaches a point where all the NaOH has been neutralized. Any excess HCl that is added beyond this point will not react with the NaOH, resulting in a decrease in the heat released during the reaction. Consequently, the temperature of the solution will start to decrease.
The decrease in temperature occurs because the excess HCl begins to act as a diluent, reducing the concentration of the neutralized NaOH and decreasing the overall heat generated. Additionally, the excess HCl can exhibit an endothermic effect, which absorbs heat from the surroundings, further contributing to the decrease in temperature.
In summary, the graph of temperature against volume of HCl will exhibit an initial increase in temperature due to the exothermic nature of the neutralization reaction. However, as excess HCl is added, the temperature will start to decrease due to the dilution effect and possible endothermic characteristics of the excess acid.