ENG_sgwhk06 - Generalized chemical reaction 0 = B B or aA +...

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1 Generalized chemical reaction aA + bB =gG + hH 0 = ∑ ν B B or 0 = ν A A + B B + G G + H H B - Chemical formula of substance ν B - Stoichiometric number: Reactant “ ”; product “ + The extent of reaction ξ≡ ———— n B –n B ° B ( B = A, B, G, H ) 1 System of pure reactants to pure products T p ξ At equilibrium only T p 2 System containing R independent reactions T p ξ 1 ξ 2 ξ 3 …… ξ R At equilibrium only T p State description of chemical reactions
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2 Molar differential change of thermodynamic quantities for chemical reaction systems U H 1. Molar differential enthalpy change for reaction of pure reactants to pure products Δ r H m =[——] T,p = ∑ ν B H * m ( B,T,p ) J.mol -1 ) ∂ξ H
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3 Δ r H m =[——] T,p = ∑ ν B H m ( B,T,p ) J.mol -1 ) ∂ξ H It is similar to the formula of molar differential enthalpy change of pure substance reactants but H m ( B,T,p ) is the partial molar enthalpy ( 偏摩尔焓 ) of substance B, i.e., 2. Molar differential enthalpy change for reaction of mixture reactants ,, (B, , ) CB B m B Tpn H HT p n ⎛⎞ = ⎜⎟ ⎝⎠
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4 3. Molar differential phase change enthalpy of substance Substance B undergoing a change from α phase to β phase can be expressed using an equation of chemical counting number of 1: B α ( T,p,n B ,…) = B β ( T,p,n B ,…) The molar differential enthalpy change is Δ α β H m =[——] T,p = H B β ( T,p,n B β ,…) - H B α ( T,p,n B α ,…) ∂ξ H If it concerns a phase change of pure substance, the H m is replaced by H m *
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5 4 Equation of thermochemistry : The equation of chemical reaction for which the reaction conditions, such as T p existing state, enthalpy change, etc., have been indicated. For example, 2C 6 H 5 COOH s, p θ ,298.15K) 15O 2 (g p θ , 298.15K) 6H 2 O l , p θ , 298.15K )+ 14CO 2 g , p θ 298.15K Δ r H m (298.15K) =- 6445.0kJ·mol 1
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6 The molar change of thermodynamic quantity of an overall reaction is the algebraic sum of the molar change of thermodynamic quantities of the individual reactions into which a reaction may be involved 5 Hess (or Γ ecc) law ( 盖斯定律 )
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7 A C ) ( m r T H Δ B ) ( m,1 r T H Δ ) ( m,2 r T H Δ Δ r H m ( T ) = Δ r H m,1 ( T ) Δ r H m,2 ( T ) If A is the algebraic sum of R reactions, the general form of Hess law will be 1 R A mi m i L L = Δ= Δ
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8 Hess law Example 1 . 298K, p θ ) ( CO ) ( O ) ( C 2 2 g g graphite + 1 1 , . J 513 . 393 θ = Δ mol k H m r (2) ) g ( ) g ( ) g ( 2 2 CO O 2 1 CO + 1 2 , . J 989 . 282 θ = Δ mol k H m r (3) ? , = Δ θ m A r H 1 2 , 1 , , . J 524 . 110 θ θ θ = Δ Δ = Δ mol k H H H m r m r m A r Example 2 . 298K, p θ ) ( NH ) ( H 2 3 ) ( N 2 1 3 2 2 g g g + ) ( H 2 3 ) ( N 2 1 ) ( NH 2 2 3 g g g + 1 , . J 19 . 46 θ = Δ mol k H m R r 1 , . J 19 . 46 θ θ = Δ = Δ mol k H H m R r m r ) ( CO ) ( O 2 1 ) ( C 2 g g graphite + (1) (1)= (2) -(3)
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9 I. Calculation of standard molar enthalpy (change) of reaction Δ r H m Θ ( T ) ( 反应的标准摩尔焓[变] ) Calculation of Δ r H m Θ ( T ) from standard molar enthalpy (change) of formation of substance B Δ f H m Θ (B,phase, T ) ( 物质
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ENG_sgwhk06 - Generalized chemical reaction 0 = B B or aA +...

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