posted by Rachel .
A student performs an experiment to determine the enthalpy of neutralization of hydrochloric acid and sodium hydroxide. The student combines 25 mL of equimolar solutions of acid and base, both having an initial temperature of 22.5 C, in an open polystyrene calorimeter. Each solution has a density of 1 g/mL and a specific heat of 4.18 J/g C. The student collects data until a maximum temperature of 26.4 C is reached. What assumption is the student allowed to make and explain how the student knows that data collection is complete.
In addition to the usual assumptions about accurately reading the thermometers, accurately measuring out the 25 mL of acid and base, etc., the student is assuming that the calorimeter has no loss of heat to the surroundings and no heat input to the calorimeter from the surroundings. The data is complete when the temperature has reached a maximum.