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

Faculty: Sarika Mehra Staff: Nirmal TA’s: Arka Sekhar Sarkar Madhusree Sarkar Manoj Patil

CL 232 TH-201: Determination of Partial Molar Enthalpies by Adiabatic Calorimetry

Objectives

 To

determine the heat capacities

• f

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

• f

enthalpy changes of chemical reactions or physical changes as well as heat capacity using the principles

• f

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 = mCpΔT + KΔT

 Heat Capacity of pure components

Q = IV t IVt = mCpΔT + KΔT

Calculations:

 Heat of mixing for different mixture compositions

Qm = (mCpm + K)(−ΔTm)

 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