Calorimetry Lab

Calorimetry
To determine the specific heat of a metal and its approximate atomic mass. To determine the heat of neutralization for a strong acid-strong base reaction. To determine the quantity and direction of heat flow for the dissolution of salt. Post Lab Questions and Answers:
1. In parts A and B in, the calorimeter, although a good insulator, absorbs some heat when the system is above room temperature. Is the reported value for the specific heat of the metal too high or too low? Explain. Is the reported DeltaHn value for the acid- base reaction too high or too low? Explain. The DeltaHn value reported in Part B will be lower than the true value because the true Delta T will never be reached. Since the calorimeter absorbs some
We were given KOH and KNO3 as our salts. We weighed the calorimeter and water then subtracted accordingly o get the mass of the calorimeter and that of the water. The lab instructed on the amounts of water and salt to be used. The initial temperature of the water in the KOH reaction was 22.8 degrees Celsius and the final temperature of the mixture determined from the graph was 37.0 degrees Celsius. The graph of the KOh showed it to be an exothermic salt and the KNO3 to be and endothermic salt because of the change in the temperature indicating either absorbing or giving off of heat by the salts. This the change in temperature of the solution of the KOH and water is + 28880 J and the heat change of the salt is 82.6 J. Thus the total heat change, in the reaction is -2960 J. To determine the DeltaHs (J/g salt), divide the totalt heat of change by the measure mass of the salt resulting in -590 J/g. The same process was followed for KNO3 but this solution had a -5.9 degree Celsius temperature change this producing a negative total heat change of water and the slat in the solution giving a +13000 J in the reaction. DeltaHs is then determines to be 250 J/g. The expected value of DeltaHs of KNO3 is +354 J/g and for KOH, -1026 J/g. The error for the KNO3 is -27.5% and for the KOH it is 42.5%. These errors are high but not uncommon for the experiment. They are caused because the salts are in a solid form and thus after the peak of temperature of solution is found, the remainder of the graph is flawed because salt is still in the process of dissolving. This dissolving still of the salts is giving off or absorbing heat thus making the extrapolated change in the temperature of solution to be small. The temperature of solution being too small results in the total heat change being too small, giving the DeltaHs value as in the case of KOH too high (not negative enough) and in the KNO3