Integral heat of mixing

Example 6.9 Four-tenths of a pound of water is mixed with 0.6 Ibm of H2SO4 to form 1.00 Ibm of 60wt% H2SO4 solution. If the starting materials and the mixed solution are all to be at 200°F, how much heat must be added or removed  

We must remove 243.2 Btu per pound of solution to hold the temperature constant.  

Example 6.10 Estimate the enthalpy of a solution of 60 wt% H2SO4 balance water at 200°E, from the partial mass enthalpies computed in Example 6.7. 

Erom Eq. 6.5, rewritten for masses instead of mols (Problem 6.9) we have 

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The integral heat of mixing is, of course, the quantity directly measured in the calorimetric method However, the heat change on diluting a solution of the polymer with an additional amount of solvent may sometimes be measured in preference to the mixing of pure polymer with solvent In either case, the desired partial molar quantity AHi must be derived by a process of differentiation, either graphical or analytical. 

Enthalpies for saturated liquids and vapors are given in Table IV for the pure components referred to zero for the liquids at 32°F. Vapor mixtures are calculated assuming zero heat of mixing. Liquid enthalpies for the mixtures are calculated to include the integral heat of mixing, given according to... 

The heat of mixing is thus equal to the variation, H, in the enthalpy which accompanies the mixing is, by definition, the integral heat of mixing, and is an extensive thermodynamic variable. 

The integral heat of mixing per mole of solution is equal to the excess enthalpy of mixing defined in the previous paragraph ... 

If partial molar heat can be obtained for each of the alloy s components, then the integral heat of mixing can be calculated and compared with that obtained from calorimetric measurements or other techniques [43] ... 

The partial or differential heat of solution, AH2, is the change in enthalpy when a very small amount of pure solute is added to a large amount of either solution or pure solvent. In the latter instance, the resultant quantity which is properly identified as the partial heat of solution at infinite dilution is sometimes referred to more simply as the heat of solution. For polymer solutions, AH 2 is often expressed as the heat absorbed per unit mass of solute added and can be found as the derivative of the integral heat of mixing ... 

Entropy The entropy of mixing pure polymer with pure solvent can be obtained firm the difference between the integral heat of mixing and the fiee energy of mixing... 

For an ideal solution the heat of mixing is zero and therefore Equation (4.1) after integrating becomes ... 

The relative integral molar enthalpy or the molar heat of mixing of liquid Sn-Bi solutions at 330°C is represented by... 

Zinc and cadmium liquid alloys conform to regular solution behaviour. The following table shows the relative integral molar enthalpies (or the molar heats of mixing) at various zinc concentrations at 723K. 

The greater the heats of mixing and differences of boiling points of the components, the greater the value of the rhs integral. In systems where this is true, this quantity is evaluated to test overall consistency. 

The molar integral heat of solution is defined as the change in enthalpy that results when 1 mole of solute (component 1) is isothermally mixed with Ni moles of solvent (component 2) and is given by... 

Integral Heat of Solution. The integral heat of solution is the heat absorbed when rii moles of component 1 is mixed with 2 moles of component 2. The enthalpy change for this process is given by... 

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