Dnyanasadhana College, Thane. hhh Department of Chemistry T.Y.B.Sc. Analytical Chemistry Paper-IV Sem-VI Thermometric Titrations Dr.Bhagure G.R. 4/27/2019

Contents 4.1.4 Thermometric Titrations –Introduction, Instrumentation, Applications in the titration of : (i) HCl v/s NaOH (ii) Boric acid v/s NaOH (iii) A mixture of Ca+2 and Mg+2 v/s EDTA (iv) Zn+2 with Disodium Tartarate. 4/27/2019

Thermometric Titrations Thermometric Titrations is defined as titration in which end point is determined by measuring the heat generated during chemical reaction 4/27/2019

Principles of Thermometric Titrations In the thermometric titration, titrant   is added at a known constant rate to a titrand until the completion of the reaction is indicated by a change in temperature. The endpoint is determined by an inflection in the curve generated by the output of a temperature measuring device 4/27/2019

aA bB pP Heat Consider the titration reaction A = the titrant, and a = the corresponding number of moles  B = the analyte, and b = the corresponding number of moles P = the product, and p = the corresponding number of moles produced 4/27/2019

At completion, the reaction produces a molar heat of reaction ΔHr which is shown as a measurable temperature change ΔT. In an ideal system, where no losses or gains of heat due to environmental influences are involved, the progress of the reaction is observed as a constant increase or decrease of temperature depending respectively on whether ΔHr is negative (indicating an exothermic reaction) or positive (indicating an endothermic reaction) 4/27/2019

THERMOMETRIC TITRATION ASSEMBLY 4/27/2019

Instrumentation of Thermometric Titrations Motor driven burette Dewar flask Thermistor Recorder 4/27/2019

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Applications of Thermometric Titrations . Applications of Thermometric Titrations .. Titration of HCl V/S NaOH … Titration of Boric acid V/S NaOH …. Titration of Calcium & Magnesium V/S EDTA 4/27/2019

Titration of HCl V/S NaOH D C Change in Temperature Δt The heat of neutralization of a fully dissociated acid with a fully dissociated base is approximately –56kJ/mol. B A Equivalence point Volume of NaOH added  4/27/2019

Titration of Boric acid V/S NaOH Change in Temperature Δt Equivalence point Volume of NaOH added  4/27/2019

Titration of Calcium & Magnesium V/S EDTA calcium reacts exothermically with EDTA (heat of chelations = -23.4 kJ/mol), magnesium reacts endothermically with a heat of chelation of = +20.1 kJ/mol B Change in Temperature Δt C A D Equ. point of Ca2+ Equ. point of Mg2+ Volume of NaOH added  4/27/2019

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