TH-201: Determination of Partial Molar Enthalpies by Adiabatic - PowerPoint PPT Presentation

CL 232 TH-201: Determination of Partial Molar Enthalpies by Adiabatic Calorimetry Faculty: Sarika Mehra Staff: Nirmal TA’s: Arka Sekhar Sarkar Madhusree Sarkar Manoj Patil

Objectives  To determine the heat capacities of pure components and binary mixtures(preferably water and light organic chemicals).  To determine heat of mixing and partial molar enthalpies of water and other component using Adiabatic Calorimetry.

Principle  Calorimetry: Involves measurement of enthalpy changes of chemical reactions or physical changes as well as heat capacity using the principles of conservation of energy.  Here Adiabatic Calorimetry is to be used.  No heat exchange with surroundings and monitoring temperature changes.

Theory  Partial molar properties are the thermodynamic properties which varies with the molar composition of the components.  It helps us to understand: • properties of components in a mixture • dominating forces (cohesive/adhesive)  Heat of mixing: The amount of heat exchanged when two components are mixed

Schematic Fig: Adiabatic Calorimeter D = Dewar Flask of capacity 150 ml, S = Polypropylene Stopper, H = Resistance Heater, ST= Stirrer, T = Temperature Sensor

Procedure:

Calculations: Determining:  Water equivalent K Q = mCp Δ T + K Δ T  Heat Capacity of pure components Q = IV t IVt = mCp Δ T + K Δ T

Calculations:  Heat of mixing for different mixture compositions Qm = (mCpm + K)(− Δ Tm)  Partial molar enthalpies at different compositions and infinite dilution H1p= Hm + x2*dHm /dx1 H2p= Hm - x1*dHm /dx1

Results and Graphs:  ΔTmix vs Mole fraction of water  Cp of mixture vs Mole fraction of water  ΔHmix vs Mole fraction of water  To comment on the nature of graphs obtained

Precautions  Since we are using an adiabatic calorimeter, temperature measurements should be constantly monitored  While heating, the mixture should be constantly stirred for temperature uniformity

Thank you