Bomb Calorimeter 1g1t6d

Bomb Calorimeter ABSTRACT: The goal of this experiment is to use temperature data over time from combustion reactions to calculate the heat released and then produce an experimental conclusion based on the achieved values through calculations. In this investigation we will measure the heat evolved during the combustion of naphthalene in the presence of excess oxygen under constant volume conditions. The main objective of this experiment is to determine the amount of water in kg equivalent to the calorimeter.

INTRODUCTION: Heat released in a chemical reaction can be determined experimentally by using an adiabatic calorimeter. The reaction must proceed without any side reactions and sufficiently fast that heat exchange with the surroundings is negligible. In such calorimeter, the combustion reaction occurs in a closed calorimeter under constant volume (bomb). The bomb is immersed in a weighted quantity of water. Continuous stirring ensures heat is distributed evenly in the calorimeter. The bomb and the water bath, which are in direct thermal , constitute an adiabatic bomb calorimeter. The heat of combustion of a substance is defined as the thermal effect that accompanies a combustion process. Upon reaction of a given substance with gaseous oxygen heat is released and specific combustion products such as carbon di oxide , nitrogen, water, sulphur di oxide are formed related to the type of substance used.

THEORETICAL BACKGROUND: Calorimetry is the study of heat transfer during physical and chemical processes. A heat transfer is always connected to a transport of energy. The total energy of a system is called its internal energy U, which is defined as the total kinetic and potential energy of the molecules in the system. A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. An adiabatic calorimeter is a calorimeter used to examine a runway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. There are 4 methods for measuring the heat in reaction calorimeter: 1, Heat flow calorimetry 2, Heat balance calorimeter 3, Power compensation 4, Constant flux.

EQUIPMENT: 1, Bomb Calorimetre including a firing mechanism. 2, Naphthalene 3, Digital thermometer 4, Stirrer 5, Pellet press 6, Ignition Wire 7, Oxygen cylinder

PROCEDURES: 1, Pallet Preparation, Care must be taken to avoid overcharging the bomb for it must be realized that the peak pressure developed during combustion is proportional to the size of the sample and to the initial oxygen pressure. Pallet size should be limited not to more than 1.1g. prepare the pallet: A, Weigh out approximately 400 milligrams of sample, grind it in a clean mortar and pestel. B, Use the pallet press to make a pellet with the ignition wire pressed at the centre of the pellet. C, Carefully place it in the bucket with tweezers, don’t touch it with your hands.

2, Ignition Wire Connection: A, The ignition wire used in the process is approximately 10cm in length. The wire is weighed before pressed within the pellet. B, Place the pallet with the ignition wire with in the bucket and place it in the bomb stand and wind the wire ends to the electrodes.

3, Liquids in the Calorimeter: Measure out 850g of water and pour it in the calorimeter jug.

4, Bomb Assembly: A, Care must be taken not to disturb the sample when sealing and charging the bomb. Slide the head assembly into the bomb cylinder, screw open vent cap on the head assembly toi allow air to be expelled, and push the head down as far into the cylinder as it will go.

B, Close the vent cap tightly. A tight seal is required to prevent oxygen leaks. C, Check the cicuit with an ohmetre. If the resistannce is too large (>>100ohms) open the bomb and check the wiring. D, Slip on the oxygen tank connection to the pin on the head assembly. E, Open the oxygen tank valve. Open the regulator valve slowly and watch the gauge as the pressure rises to the desired filling pressure. Once the pressure is reached the mark close the control valve and then the tank vavle. NOTE: If the bomb is filled too quickly you can blow your sample out of the sample cup. Donot exceed the specified pressure. F, Use the quick release valve to quickly remove the oxygen tank connection to minimize oxygen escape. Slightly leakage is normal but continuous leakage is a problem.

5, Operating The Calorimeter: A, Carefully place the charged bomb in the bucket, noting that it rests on the raised circular area on the bottom of the bucket. B, Turn on the magnetic stirrer and place in the node of the digital thermometer and after 2 minutes take down initial temperature readings of the water in the jug. C, Connect the positive and negative terminal of the power supply to the socket on the bomb. And carefully turn it on.

DATA ANALYSIS: Mass of the iron wire ma=2.5x10-5kg. Mass of the naphthalene pellet with wire, mb=0.44x10-3. Initial Temperature of the calorimeter, T1=27.3oC. Final Temperature, T2=30.50C. Calculation: Mass of burnt fuel, mN= mb -ma = 4.2x10-4kg. Temperature difference= 3.20C. Water equivalent of the calorimeter(W),

DISCUSSIONS AND CONCLUSIONS:

A1: