Moles of solute

Langmuir [ 146] gave an instructive interpretation to this rule. The work W to transfer one mole of solute from bulk solution to surface solution should be... 

Procedure. Calculate the heats of solution of the two species, KF and KF HOAc, at each of the four given molalities from a knowledge of the heat capacity. Calculate the enthalpy of solution per mole of solute at each concentration. Find... 

The cryoscopic constant Kj gives the depression of the melting point AT (in degrees Celsius) produced when 1 mol of solute is dissolved in 1000 g of a solvent. It is applicable only to dilute solutions for which the number of moles of solute is negligible in comparison with the number of moles of solvent. It is often used for molecular weight determinations. 

Both molarity and formality express concentration as moles of solute per liter of solution. There is, however, a subtle difference between molarity and formality. Molarity is the concentration of a particular chemical species in solution. Formality, on the other hand, is a substance s total concentration in solution without regard to its specific chemical form. There is no difference between a substance s molarity and formality if it dissolves without dissociating into ions. The molar concentration of a solution of glucose, for example, is the same as its formality. 

The number of moles of solute, regardless of chemical form, per liter of solution (F). 

Conservation of mass requires that the moles of solute initially present in one phase equal the combined moles of solute in the aqueous and organic phases after the extraction thus... 

Since 40.0% of the solute remains in the aqueous phase, and 60.0% has been extracted into the organic phase, the moles of solute in the two phases after extraction are... 

Solving equation 12.3 for the moles of solute in the stationary phase and substituting into equation 12.2 gives... 

Electrokinetic injections are made by placing both the capillary and the anode into the sample vial and briefly applying an electric fleld. The moles of solute injected into the capillary, nj, are determined using... 

Multiplying and dividing the right-hand side by Ni -t- N2 and letting this sum equal Avogadro s number of molecules gives per mole of solution ... 

We can shift from numbers of molecules to numbers of moles of solute by dividing by Avogadro s number and changing k to R. Also, recalling that V = SjnjVj, we write... 

It is conventional to use molality—moles of solute per kilogram of solvent (symbol m)—as the concentration unit in electrolyte thermodynamics. Accordingly, we shall represent the concentrations of both the indifferent electrolyte and the polymer in these units in this section m3 and m2, respectively. In the same dilute (with respect to polymer) approximation that we have used elsewhere in this chapter, m2 is related to the mass volume system of units C2 by... 

Concentration. The basis unit of concentration in chemistry is the mole which is the amount of substance that contains as many entities, eg, atoms, molecules, ions, electrons, protons, etc, as there are atoms in 12 g of ie, Avogadro s number = 6.0221367 x 10. Solution concentrations are expressed on either a weight or volume basis. MolaUty is the concentration of a solution in terms of the number of moles of solute per kilogram of solvent. Molarity is the concentration of a solution in terms of the number of moles of solute per Hter of solution. 

Fig. 2. Schematic representation of relevant electrolyte transport through the renal tubule, depicting the osmolar gradient ia medullary iaterstitial fluid ia ywOj yW where represents active transport, —passive transport, hoth active and passive transport, and passive transport of H2O ia the presence of ADH, ia A, the cortex, and B, the medulla. An osmole equals a mole of solute divided by the number of ions formed per molecule of the solute. Thus one mole of sodium chloride is equivalent to two osmoles, ie, lAfNaCl = 2 Osm NaCl. ADH = antidiuretic hormone.

Consider the entropy change in forming one mole of solution at constant T from 4>m moles of 1 (of molar volume V ) and ni2 moles of 2 (of molar volume V2). In the pure state, the 0m 1 moles of 1 occupy (or have available) the volume 0mIF], and the 0m2 moles of 2 have available the volume 0m2 2- However, when the solution is formed, both the 0m 1 moles of 1 and the 0m2 moles of 2 have available to them the entire volume of the solution 0mi V +0m2 2- The entropy change experienced by component 1 due to this available volume change is... 

Generally, these concentrations are expressed in terms of moles of solute per mole of pure solvent (liquid phase) and moles of solute per mole of inert gas (gas phase), thus making the material balance calculations easier. 

Reality Check The molarity decreases when water is added. The moles of solute stay the same, but the volume of the solution increases. 

Strategy To go from concentration of solute to concentration of an individual ion, you must know the conversion factor relating moles of ions to moles of solute. To find this conversion factor, it is helpful to write the equation for the solution process. 

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