CHEMICAL THERMODYNAMICS 1 chem 16 4 slides per page

Standard p 10000 bar be careful not to confuse these

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Unformatted text preview: r MgCl2(s) is: Thermochemical Standard States ∆Horxn Thermochemical standard state conditions Standard T = 298.15 K (depends on the temp condition of tabulated values). Standard P = 1.0000 bar. Be careful not to confuse these values with STP. Thermochemical standard states of matter Standard state of pure matter – the pure liquid or solid form. Gases –1.00 bar of pressure. For gaseous mixtures - partial pressure =1.00 bar. Aqueous solutions – 1.00 M concentration. Standard Molar Enthalpies of Formation, ∆Hfo • Standard molar enthalpy of elements in their most stable forms at 298.15 K and 1.000 atm is zero. – Reference state for all enthalpy calculations are the constituent elements of the compound. Elements Ca(s) C(s) (graphite) H+(aq) Br2(l) I2(s) S?(?) Hg(?) ∆Hfo kJ/mole 0 0 0 0 ∆Hfo of elements in their standard states: 0 0 0 0 5 1/7/2014 • ∆Hfo of all compounds, ions and elements in their non-standard states: Nonzero value Compound CaF2(s) C(s) (diamond) HNO3(aq) HNO3(l) H2O(g) H2O(l) Au(g) Cu2+(aq) ∆Hfo kJ/mole -1219.6 +1.895 -207.36 -205.0 -241.82 -285.83 +366.1 +64.77 Using Enthalpies of Formation Standard Molar Enthalpies of Formation, ∆Hfo Example: The standard molar enthalpy of formation for phosphoric acid is -1281 kJ/mol. Write the thermochemical balanced equation for the formation of H3PO4 P in standard state is P4 Phosphoric acid in standard state is H3PO4(s) Using Enthalpies of Formation • For any process (can be reactions, physical changes, or transformations) xA + yB nC + mD • Set-up the equation for Enthalpy of Reaction in: 2H2(g) + O2(g) 2H2O(l) at 25oC ∆Hrxno = (2 • ∆Hf, H2O(l)o ) – (2 • ∆Hf, H2(g)o + ∆Hf, O2(g)o ) ∆Hprocess = ∑(coefficients•∆Hfproducts) – ∑(coefficients•∆Hfreactants) Set-up the equation for Enthalpy of Vaporization in: H2O(l) H2O(g) at 25oC o = (1 • ∆H o o ∆Hvap f, H2O(g) ) – (1 • ∆Hf, H2O(l) ) ∆Hprocess = (n•∆HfC + m•∆HfD) – (x•∆HfA + y•∆HfB) Set-up the equation for Enthalpy...
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This document was uploaded on 03/26/2014.

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