Sulfuric acid molality

Table 1 gives the calculated open circuit voltages of the lead—acid cell at 25°C at the sulfuric acid molalities shown. The corrected activities of sulfuric acid from vapor pressure data (20) are also given. 

Relative partial molar enthalpies can be used to calculate AH for various processes involving the mixing of solute, solvent, and solution. For example, Table 7.2 gives values for L and L2 for aqueous sulfuric acid solutions7 as a function of molality at 298.15 K. Also tabulated is A, the ratio of moles H2O to moles H2S(V We note from the table that L — L2 — 0 in the infinitely dilute solution. Thus, a Raoult s law standard state has been chosen for H20 and a Henry s law standard state is used for H2SO4. The value L2 = 95,281 Tmol-1 is the extrapolated relative partial molar enthalpy of pure H2SO4. It is the value for 77f- 77°. 

Table 7.2 Partial molar thermal properties for aqueous sulfuric acid solutions at T = 298.15 K. m is the molality of the H1SO4 and A is the ratio (moles FFO/moles...

Values taken from S. Glasstone. Thermodynamics for Chemists. D. Van Nostrand Company Inc., Toronto, p. 443 (1947). The values tabulated in this reference were taken from D. N. Craig and G. W. Vinal, J. Res. Natl. Bur. Stand.. Thermodynamic Properties of Sulfuric Acid Solutions and Their Relation to the Electromotive Force and Heat of Reaction of the Lead Storage Battery", 24, 475-490 (1940). More recent values at the higher molality can be found in W. F. Giauque. E. W. Hornung. J. E. Kunzler and T. R. Rubin, The Thermodynamic Properties of Aqueous Sulfuric Acid Solutions and Hydrates from 15 to 300° K", J. Am. Chem. Soc.. 82, 62-70 (1960). 

Figure 1. Osmotic coefficient of aqueous sulfuric acid (up to 2m) at 298 K as a function of the square-root of molality ((Q) Pitzer evaluation ( -) experimental...

Figure 18.2. Nonlinear dependence of volume on molality for dilute solutions of sulfuric acid (H2SO4) in water (H2O). Based on data of I. M. Klotz and C. F. Eckert, J. Am. Chem. Soc. 64, 1878 (1942).

For example, the observation that the freezing point of a 1 molal solution of acetone in sulfuric acid is depressed by twice the molal freezing-point depression constant of sulfuric acid is interpreted in terms of the reaction... 

What is the molality of the 16.0 mass % solution of sulfuric acid in Problem 11.60 ... 

Calculate the (a) molar concentration and (b) molality of a sulfuric acid solution of density 1.198 g/mL containing 27.0% H2SO4 by weight. 

Sulfuric acid has received considerable study as a nonaqueous solvent (see Chapter 5). It is, of course, a strongly acidic solvent, and it has a Kf value of -6.15 °/molal. In 100% H2S04, conductivity measurements and cryoscopic studies show that protonation of many substances occurs even though they are not normally bases in the usual sense. For example, organic compounds such as acetic acid and ether function as proton acceptors ... 

The cryoscopic method was used in Hantzsch s original work 53, 54) and was later developed by Hammett and Deyrup 56) and by Gillespie et al. 48). Sulfuric acid freezes at 10.371 C and has a relatively large molal freezing-point depression or cryoscopic constant fc = 6.12 32). It is thus a convenient solvent for cryoscopic measurements provided that adequate precautions are taken to prevent absorption of water from the atmosphere. From freezing-point measurements the number, v, of moles of particles (ions and molecules) produced by one mole of any solute may be obtained. Some examples are given in Table IV. 

A 9.386 M aqueous solution of sulfuric acid has a density of 1.5091 g cm. Calculate the molality, the percentage by mass, and the mole fraction of sulfuric acid in this solution. 

The relative apparent molar heat contents of sulfuric acid (solute) in mixtures with water (solvent), for various compositions at 25° C, are recorded in Table XXXVl. It may be noted that when L is positive, is negative, and the dilution process is accompanied by the evolution of heat. It is seert, therefore, from Table XXXVI that heat is evolved upon the infinite dilution of sulfuric acid solutions at all concentrations down to the lowest studied, viz., 0.00108 molal. 

Problem Assuming to remain constant, calculate the relative change in the mean ionic activity coefficient of 1 molal sulfuric acid solution from 0 to 25 C. 

The E.M.F. of a lead storage battery containing 2.75 molal sulfuric acid was found to be 2.005 volt at 25 C. The aqueous vapor pressure of the acid solution at this temperature is about 20.4 mm., while that of pure water is 23.8 mm. The mean ionic activity coefficient of the sulfuric acid is 0.136. Calculate the standard free energy change of the cell reaction at 25 C and check the values from tabulated free energy data. 

Calculate the molality of a sulfuric acid solution containing 24.4 g of sulfuric acid in 198 g of water. The molar mass of sulfuric acid is 98.08 g. 

Answer From the known molar mass of sulfuric acid, we can calculate the molality in two steps. First we need to find the number of grams of sulfuric acid dissolved in 1000 g (1 kg) of water. Next we must convert the number of grams into the number of moles. Combiiung these two steps we write... 

The concentrated sulfuric acid we use in the laboratory is 98.0 percent H2SO4 by mass. Calculate the molality and molarity of the acid solution. The density of the solution is 1.83 g/mL. 

The concentration of commercially available concentrated sulfuric acid is 98.0 percent by mass, or 18 M. Calculate the density and the molality of the solution. 

The activity of any ion, a = 7m, where y is the activity coefficient and m is the molality (mol solute/kg solvent). Because it is not possible to measure individual ionic activities, a mean ionic activity coefficient, y , is used to define the activities of all ions in a solution. The convention used in most of the literature to report the mean ionic activity coefficients for sulfuric acid is based on the assumption that the acid dissociates completely into hydrogen and sulfate ions. This assumption leads to the following formula for the activity of sulfuric acid. 

The electrolyte in automobile lead storage batteries is a 3.75Msulfuric acid solution that has a density of 1.230 g/mL. Calculate the mass percent, molality, and normality of the sulfuric acid. 

Strategy In solving this type of problem, it is convenient to assume that we start with 100.0 grams of the solution. If the mass of sulfuric acid is 98.0% of 100.0 g, or 98.0 g, the percent by mass of water mnst be 100.0% - 98.0% = 2.0%. The mass of water in 100.0 g of solntion would be 2.0 g. From the definition of molality, we need to find moles of solute (sulfuric acid) and kilograms of solvent (water). 

Electrochemical equivalent of sulfuric acid solution vs solution density and molality. 

A sulfuric acid solution containing 571.6 g of H2SO4 per liter of solution has a density of 1.329 g/cm. Calculate (a) the mass percentage, (b) the mole fraction, (c) the molality, (d) the molarity of H2SO4 in this solution. 

Tellurium dioxide (0.5 g.) is dissolved in 5 ml. of 40 per cent hydrobromic acid. A saturated solution of two molal equivalents of potassium bromide (0.75 g. in about 1.4 ml. of water) is then added. The solution is evaporated on a steam bath and stirred until the orange crystals settle well. The salt is recrystalhzed from boiUng water containing 5 to 10 per cent hydrobromic acid and is dried in a vacuum desiccator over soda lime and finally over sulfuric acid. Yield 1.60 g. (75 per cent). 

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