Aqueous solutions heat capacity

The estimation of the aqueous solubility at rmin and at other temperatures requires data on the enthalpy and the heat capacity of the solution. These properties are themselves temperature dependent and have been systematically studied for various sets of compounds such as hydrocarbons [58,59], 1-alkanols [60], alkoxyethanols, and 1,2-dialkoxyethanes [61], carboxylic acids, amines, and N-substituted amides [62], monoesters, ethylene glycol diesters, glycerol triesters [63], and crown ethers [64], Additive schemes for the estimation of aqueous solution heat capacities have been evaluated [65,66],... 

The techniques used in the critical evaluation and correlation of thermodynamic properties of aqueous polyvalent electrolytes are described. The Electrolyte Data Center is engaged in the correlation of activity and osmotic coefficients, enthalpies of dilution and solution, heat capacities, and ionic equilibrium constants for aqueous salt solutions. 

The ionization potentials of some of the bipyridines have been investigated. Solubility data for 2,2 -bipyridine in aqueous solution, in aqueous solvent mixtures, and in various aqueous salt solutions have been obtained, whereas the heat of solution, heat capacities, and related data for 2,2 - and 4,4 -bipyridines in water have been measured. The enthalpies of solution of 2,2 -bipyridine in water and aqueous solvent mixtures have also been obtained. Dielectric relaxation studies of 2,2 -bipyri-dine in carbon tetrachloride have been reported in connection with hindered internal rotation. Partition coefficients for 2,2 -bipyridine between water and various organic solvents have been measured. ... 

Use the heat of solution data in Table B.IO and solution heat capacity data to (a) calculate the enthalpy of a hydrochloric acid, sulfuric acid, or sodium hydroxide solution of a known composition (solute mole fraction) relative to the pure solute and water at 25 C (b) calculate the required rate of heat transfer to or from a process in which an aqueous solution of HCl, H2SO4, or NaOH is formed, diluted, or combined with another solution of the same species and (c) calculate the final temperature if an aqueous solution of HCl, H2SO4, or NaOH is formed, diluted, or combined with another solution of the same species adiabatically. Perform material and energy balance calculations for a process that involves solutions for which enthalpy-concentration charts are available. 

HEAT OF SOLUTION. HEAT CAPACITY. AND DENSITY OF AQUEOUS FORMAMIDE SOLUTIONS AT 25 C. 

Aqueous ions heat capacity, osmotic coefficient, entropy The heat capacities and osmotic coefficients of aqueous solutions of some salts of most of the ions have been determined by Spedding and others (Rard 1985,1987). 

Figure 5.1 is a graph of the specific heat capacity cp (heat capacity per gram) of aqueous sulfuric acid solutions at T — 298.15 K against A, the ratio of moles of water to moles of sulfuric acid. The values plotted were obtained from a very... 

Example 5.1 The apparent molar heat capacities at 298.15 K of HNO3 in aqueous nitric acid solutions are given by the expression5... 

Table 9.2 Standard heat capacities, entropies, enthalpies, and Gibbs free energies of formation of some common ions in aqueous solution at T= 298.15 K...

There are two steps in the calculation. First, calibrate the calorimeter by calculating its heat capacity from the information on the first reaction, Cca) = qc, /AT. Second, use that value of Cc-1 to find the energy change of the neutralization reaction. For the second step, use the same equation rearranged to gcal = Cca AT, but with AT now the change in temperature observed during the reaction. Note that the calorimeter contains the same volume of liquid in both cases. Because dilute aqueous solutions have approximately the same heat capacities as pure water, assume that the heat capacity is the... 

The mechanisms that affect heat transfer in single-phase and two-phase aqueous surfactant solutions is a conjugate problem involving the heater and liquid properties (viscosity, thermal conductivity, heat capacity, surface tension). Besides the effects of heater geometry, its surface characteristics, and wall heat flux level, the bulk concentration of surfactant and its chemistry (ionic nature and molecular weight), surface wetting, surfactant adsorption and desorption, and foaming should be considered. 

What is the evaporation rate and yield of the sodium acetate hydrate CH3C00Na.3H20 from a continuous evaporative crystalliser operating at 1 kN/m2 when it is fed with 1 kg/s of a 50 per cent by mass aqueous solution of sodium acetate hydrate at 350 K The boiling point elevation of the solution is 10 degK and the heat of crystallisation is 150 kJ/kg. The mean heat capacity of the solution is 3.5 kJ/kg K and, at 1 kN/m2, water boils at 280 K at which temperature the latent heat of vaporisation is 2.482 MJ/kg. Over the range 270-305 K, the solubility of sodium acetate hydrate in water s at T(K) is given approximately by ... 

Criss, C. M. Cobble, J. W. "The Thermodynamic Properties of High Temperature Aqueous Solutions. V. The Calculation of Ionic Heat Capacities up to 200OC. Entropies and Heat Capacities above 200 C" J. An. Chan. Soc., 1964, 86, 5390. 

The mass, m, is the mass of the solution, because the solution absorbs the heat. When a dilute aqueous solution is used in a calorimeter, you can assume that the solution has the same density and specific heat capacity as pure water. As you saw above, you can also assume that the heat capacity of the calorimeter is negligible. In other words, you can assume that all the heat that is released or absorbed by the reaction is absorbed or released by the solution. 

A solution of 0.54 g. (2 mmoles) of ferric chloride hexahydrate and 0.33 g. (3 mmoles) of diethylammonium chloride (Note 1) in 5 g. of methanol is added to a solution of 11.2 g. (0.1 mole) of 1-octene (Note 2) and 0.42 g. (2 mmoles) of benzoin (Note 3) in 36 g. (0.3 mole) of chloroform (Note 4). The resulting homogeneous mixture is introduced into a Carius tube of about 100-ml. capacity. Air is displaced by dropping a few pieces of dry ice into the tube (Note 5). The tube is sealed (Note 6), heated to 130°, kept at that temperature for 15 hours, cooled to room temperature (Note 7), and opened. The contents of the tube are transferred to a separatory fuimel, and the tube is rinsed with about 10 ml. of chloroform. The reaction mixture is washed with 40 ml. of water. The aqueous solution is extracted with 10 ml. of chloroform, and the extract is added to the original chloroform layer. Solvent is distilled at atmospheric pressure (bath temperature up to 130°). The distillation flask is allowed to cool, and distillation is continued at 25 mm. (bath temperature up to 120°) (Note 8). The flask is cooled again, and distillation is continued to dryness at 0.1 mm. (bath temperature up tc 150°), giving crude l,l,3-trichloro- -nonane (19.4 g.) as a yellow oil, b.p. 60-85° (0.1 mm.), 1.4650. The purity of this... 

Heat capacity data for ions in aqueous solution over the temperature range 25-200°C. Such data for ionic species of uranium, plutonium, other actinides and various fission products such as cesium, strontium, iodine, technetium, and others are of foremost interest. 

However, two types of systems are sufficienfry important that we can use them almost exclusively (1) liquid aqueous solutions and (2) ideal gas mixtures at atmospheric pressure, hr aqueous solutions we assume that the density is 1 gtcvc , the specific heat is 1 cal/g K, and at any solute concentration, pressure, or temperature there are -55 moles/hter of water, hr gases at one atmosphere and near room temperature we assume that the heat capacity per mole is R, the density is 1/22.4 moles/hter, and aU components obey the ideal gas equation of state. Organic hquid solutions have constant properties within 20%, and nonideal gas solutions seldom have deviations larger than these. 

For liquid water and for aqueous solutions we wiU assume Cp = 1 cal/g K, and, since the density p of water is -1 g/cm, we have pCp = 1 cal/cm K or pCp =1000 cal/Uter K. To estimate the heat capacity of gases, we will usually assume that the molar heat capacity Cp is j R cal/mole K. There are thus three types of heat capacity, the heat capacity per unit mass Cp, the heat capacity per unit volume pCp, and the heat capacity per mole Cp. However, we will use heat capacity per unit volume for much of the next two chapters, and we use the symbol pCp for most of the equations. 

Medium-chain alcohols such as 2-butoxyethanol (BE) exist as microaggregates in water which in many respects resemble micellar systems. Mixed micelles can be formed between such alcohols and surfactants. The thermodynamics of the system BE-sodlum decanoate (Na-Dec)-water was studied through direct measurements of volumes (flow denslmetry), enthalpies and heat capacities (flow microcalorimetry). Data are reported as transfer functions. The observed trends are analyzed with a recently published chemical equilibrium model (J. Solution Chem. 13,1,1984). By adjusting the distribution constant and the thermodynamic property of the solute In the mixed micelle. It Is possible to fit nearly quantitatively the transfer of BE from water to aqueous NaDec. The model Is not as successful for the transfert of NaDec from water to aqueous BE at low BE concentrations Indicating self-association of NaDec Induced by BE. The model can be used to evaluate the thermodynamic properties of both components of the mixed micelle. 

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