One Page Thermo

Thermodynamics in One Page Some of this (most of this) was obtained from the CLC Work • 1 st Law of Thermodynamics: energy is conserved ΔE =q+w • ΔE = internal energy, q=heat, w=work • Heat: q<0 (-) exothermic (gives off) & q>0 endothermic (absorbs) • Work: defined as PV work w=-PΔV from w=-PΔV when ΔV>0 (+) w<0 (-) Work is done by the system when ΔV<0 (-) w>0 (+) Work is done on the system Heat of Formation ΔH f O required to make 1 mole of substance from its elements in their standards states (note ΔH f for elements is 0) ΔH rxn = ΣnΔH f (products) –ΣnΔH f (reactants) Standard States F 2 ,Cl 2 ,Br 2 ,I 2 ,H 2 , N 2 ,O 2 ,He, Ne, Ar, Kr, Rn are gases Br 2 and Hg are liquid Everything else is solid. Carbon is C graphite Enthalpy • Defined as H=E+PV where E is internal energy and PV is work • Change is enthalpy at constant pressure is ΔH=ΔE+PΔV • ΔH = q p where q p is heat at constant pressure • ΔE = q v where q v is heat at constant volume • To relate q p and q v q p = q v – w Hess’s Law: If 2 or more reactions are added, the overall ΔH rxn is the sum of the ΔH rxn for each of the reactions used. 1. Multiply a reaction by a coefficient, c ΔH new = c(ΔH rxn ) 2. Reverse a reaction: change the sign of ΔH ΔH new = -(ΔH rxn ) 3. Add reactions: add ΔH values ΔH total = ΔH 1 +ΔH 2 +ΔH 3 +… Calorimetry heat lost = heat gained q rxn = -q solution m 1 c 1 ΔT 1 = m 2 c 2 ΔT 2

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Gen Chem

Transcript of One Page Thermo

Thermodynamics in One PageSome of this (most of this) was obtained from the CLC

Work 1st Law of Thermodynamics: energy is conserved E =q+w E = internal energy, q=heat, w=work Heat: q0 endothermic (absorbs) Work: defined as PV work w=-PV

from w=-PV when V>0 (+) w