Bomb Calorimeter ,Construction,Working And Calculation

Bomb Calorimeter , Construction, Working, And Calculations

Purpose: The purpose of the bomb calorimeter is to find the calorific value of solid and liquid fuels.

Construction of Bomb Calorimeter: A bomb calorimeter made of several parts . The outer most cylindrical stainless steel called bomb in which combustion of fuel (solid/liquid) takes place.The cylindrical stainless steel is covered with lid to make it air tight so that no combustion gas produced by the fuel leak. In the lid spacing is provided for the two stainless steel electrodes and oxygen valve (provide oxygen for combustion).The bomb is placed in copper calorimeter which is surrounded by the water and air jacket to prevent heat losses due to radiation.The calorimeter contain a thermometer called Beckmann's Thermometer which can read 1/100th of temperature difference in degree.

Working of Bomb Calorimeter: In this, a known mass of fuel (liquid / solid) is placed in the clean crucible . Then we place a magnesium wire that is stretched between the two electrodes and the magnesium wire touching the fuel . With the help of oxygen valve, 25 atmospheric pressure is created inside the cylinder to make sure no gas leakage will occur lid is tightly screwed. The bomb is then placed in a copper calorimeter with a known mass of water present in it. Then we will start the stirrer and note down the Beckmann's thermometer initial temperature. Then we connect our wire with a 6V battery will cause combustion in the bomb stirrer is rotating so that the temperature remains the same throughout the water. After combustion maximum temperature is noted down.

Calculations : Let x = mass(gram) of fuel sample taken

W = mass of water in the calorimeter

w = water equivalent(gram) of calorimeter ,stirrer ,thermometer ,bomb etc

t1 = Initial temperature of water in calorimeter (Before combustion)

t2 = Final temperature of water in calorimeter (After combustion)

L = Higher Calorific Value in fuel cal/g

Heat produced by the fuel (solid/liquid) = xL

Heat absorbed by water = (W+w)(t2-t1)

xL = (W+w)(t2-t1)

L = (W+w)(t2-t1)/x          cal/g