Experiment 28March 23, 2010

Dr. Scott Buzby, Ph.D.

To measure, using a calorimeter, the energy changes accompanying neutralization reactions

Learn the Kelvin temperature scale

Define heat capacity

The kelvin (K) is a unit increment of temperature and is one of the seven SI base units (meter, kilogram, second, mole, ampere & candela)

The Kelvin scale is a thermodynamic (absolute) temperature scale referenced to absolute zero, the theoretical absence of all thermal energy

By definition it is zero kelvins (0 K) 1 Kelvin = 1° Celsius

Every chemical reaction is accompanied by a change in energy, usually in the form of heat

The energy change of a reaction is called the Heat of Reaction or the Enthalpy Change (H)

If heat is evolved, the reaction is exothermic and H < 0

If heat is absorbed, the reaction is endothermic and H > 0

Tonight we will measure the heat of neutralization when an acid and a base react to form water

This is measured by allowing the reaction to take place in a thermally insulated vessel called a calorimeter

The heat given off by the reaction will cause an increase in the temperature of the solution and the calorimeter

If the calorimeter was perfect, no heat would be by the calorimeter or the laboratory

In order to determine the heat of reaction we must first determine the amount of heat absorbed and the heat capacity of the calorimeter

Heat capacity of the calorimeter is the amount of heat (in joules) needed to raise its temperature by 1 kelvin

The heat capacity of a calorimeter is determined by measuring the temperature change that occurs when a known amount of hot water is added to a known amount of cold water

The heat lost by the hot water is equal to the heat gained by the cold water and the calorimeter

Procedure on top of Page 322 Graph Temperature vs. Time for hot and

cold water Do the calculations on the report sheet

Page 320-321 and example 28.1 for help

Procedure: Part B – Page 322 Part C – Page 323

Graph Temperature vs. Time for solution Do the calculations on the report sheet

Page 320-321 and example 28.2 for help

Report Sheet – Pages 325-327 Questions – Page 327 Three Graphs – Pages 328-330 or print-

outs Pre-Lab Experiment 33 – Page 427

Reminder – Course evaluations will be next week