2 Thermodynamics & Kinetics-Calorimetry, Lecture notes of Chemistry

Download 2 Thermodynamics & Kinetics-Calorimetry and more Lecture notes Chemistry in PDF only on Docsity! 5.60 Spring 2007 Lecture #7 page 1 Calorimetry The objective is to measure ( )Δ 1rx TH Reactants (T1) = isothermal constant p Products (T1) • Constant pressure (for solutions) adiabatic constant preaction calorimeter I) React. (TΔ IH 1) + Cal. (T1) = adiabatic constant p Prod. (T2) + Cal. (T2) II) Prod. (TΔ IIH 2) + Cal. (T2) = constant p Prod. (T1) + Cal. (T1) ______________________________________________________ ( )Δ 1rx TH React. (T1) + Cal. (T1) = constant p Prod. (T1) + Cal. (T1) ( ) = +Δ Δ Δ1rx I ITH H IH (I) Purpose is to measure (T2 - T1) Adiabatic, const. p = =⇒ ⇒ Δ0 0 p Iq H (II) Purpose is to measure heat qp needed to take prod. + cal. from T2 back to T1. ( ) ( ) ( ) = + = = − + Δ ∴ Δ ∫ ∫ 2 1 2 1 1 Pr . . Pr . . T p p IIT T rx pT q C od Cal dT T C od Cal H H dT 5.60 Spring 2007 Lecture #7 page 2 • Constant volume (when gases involved) adiabatic constant Vreaction calorimeter I) React. (TΔ IU 1) + Cal. (T1) = adiabatic constant V Prod. (T2) + Cal. (T2) II) Prod. (TΔ IIU 2) + Cal. (T2) = constant V Prod. (T1) + Cal. (T1) ______________________________________________________ ( )Δ 1rx TU React. (T1) + Cal. (T1) = constant V Prod. (T1) + Cal. (T1) ( ) = +Δ Δ Δ1rx I ITU U IU (I) Purpose is to measure (T2 - T1) Adiabatic, const. V = =⇒ ⇒ Δ0 0 IVq U (II) Purpose is to measure heat qV needed to take prod. + cal. from T2 back to T1. ( ) ( ) ( ) = + = = − + Δ ∴ Δ ∫ ∫ 2 1 2 1 1 Pr . . Pr . . T IIV VT T rx VT q C od Cal dT T C od Cal U U dT Now use ( )+= + Δ = Δ Δ or H U pV H U pV Assume only significant contribution to ( )Δ pV is from gases. Ideal gas ( ) ( )=⇒ Δ Δ RpV nT