Hydrochloric acid enthalpy

Use the data provided in Appendix 2A to calculate the standard reaction enthalpy for the reaction of calcite with hydrochloric acid ... 

Thus in hydrochloric acid medium, potassium hexacyanoferrate (111) is thought to give cyanoferric acid, which has a very endothermic enthalpy of formation (AHf = 534.7 kJ/mol 2.48 kJ/g), explaining the explosive property. 

Background Thermochemistry is the study of heat changes and transfers associated with chemical reactions. In this thermochemical laboratory study, you will determine the enthalpy change that occurs when a strong base, sodium hydroxide, reacts with a strong acid, hydrochloric acid. Other mixtures studied will include ammonium chloride mixed with sodium hydroxide and ammonia mixed with hydrochloric acid. These three reactions are represented as ... 

Fig. 1. Enthalpies of solution of lanthanide trihalides in aqueous media ( ) anhydrous trichlorides (183) and trichloride hexahydrates (189) in water (A) trichloride hex-ahydrates in dilute hydrochloric acid (190) ( ) trichloride hexahydrates in aqueous magnesium chloride solution (191) ( ) anhydrous triiodides in water (192). Values for the trichlorides refer to 25°C, for the triiodides to 20°C. Filled symbols represent experimental determinations, open symbols represent estimates.

Hproblems associated with all the trihalides of this review of the presence of small amounts of hydrates or oxochlorides. While on the matter of possible impurities, it may be recalled that in Bommer and Hohmann s early work there is a discrepancy between enthalpies of solution of anhydrous trichlorides and of respective metals in hydrochloric acid. Here the more likely impurity to be responsible is unreacted potassium metal in the lanthanide metal used in the hydrochloric acid dissolution experiments. 

Enthalpies op Solution of Anhydrous Trichlorides in Aqueous Hydrochloric Acid (at 25°C) ... 

Enthalpies of solution of lanthanum (180) and scandium (208) trichlorides in 14.1% and in 0.5 M aqueous hydrochloric acid, respectively, are also smaller than the respective enthalpies of solution in water. In the former case the values - 26.4 and — 31.6 kcal mol-1 were measured at 20°C in the latter, a value of — 43.0 kcal mol-1 for dissolution in hydrochloric acid at 25°C has to be compared with a value of -47.1 kcal mol-1 for dissolution in water at 20°C (180). Enthalpies of... 

Fig. 2. The variation of the enthalpies of solution of lanthanide trichlorides and, for comparison, indium trichloride (dashed line), with acid concentration in aqueous hydrochloric acid, at 25°C (182b).

Enthalpies of solution of the series of chloride hydrates in aqueous hydrochloric acid (approximately 0.1 mol dm-3) are listed in Table IX (190). In Fig. 1, the trend in these values across the lanthanide series is compared with the trends for enthalpies of solution of the hydrates and of the anhydrous salts in water. 

Since this review was written, enthalpies of solution of several lanthanide tribro-mides in various concentrations of hydrochloric acid have been reported [C. Hurtgen, D. Brown, and J. Fuger, J. Chem. Soc. Dalton Trans, p. 70 (I960)]. 

How can the enthalpy changes for two chemical reactions be used to obtain the enthalpy change for the reaction of ammonia with hydrochloric acid NH3(aq) + HCI(aq) NH CKaq)... 

When strong bases neutralize strong acids in solutions that have molar concentrations of 1 mol dm-3, the enthalpy of the reaction is observed to be -55.83 kJ mol - irrespective of the counter ions (e.g. the chloride ion derivable from HC1 and the sodium ion contained in NaOH) present. For example, when a standard solution (1 mol dm-3) of hydrochloric acid is neutralized by a standard solution (1 mol dm-3) of sodium hydroxide, the change in enthalpy of the reaction is -55.83 kJ mol-1. Because the strong acid HCI and the strong base NaOH are 100% dissociated in aqueous solution, theucutruli/atiun reaction may be written as ... 

The mean ionic activity coefficients of hydrobromic acid at round molalities (calculated by means of Equation 2) are summarized in Tables XI, XII, and XIII for x = 10, 30, and 50 mass percent monoglyme. Values of —logio 7 at round molalities from 0.005 to 0.1 mol-kg-1 were obtained by interpolating a least squares fit to a power series in m which was derived by means of a computer. These values at 298.15° K are compared in Figure 2 with those for hydrochloric acid in the same mixed solvent (I) and that for hydrobromic acid in water (21). The relative partial molal enthalpy (H2 — Hj>) can be calculated from the change in the activity coefficient with temperature, but we have used instead the following equations ... 

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. 

Use Table B.ll to determine the specific enthalpy (kJ/mol HCl) of hydrochloric acid containing... 

The enthalpy of reaction of KBH (cr) with hydrochloric acid has been measured by solution calorimetry and reported by Johnson, Schumm, Wilson, and Prosen (4). 

The enthalpies of solution and reaction of LiF(cr) in water and hydrochloric acid have been measured by many investigators. The reported values are listed in the table below. Using A H (Li, aq, , 298.15 K) = -66.56 kcal mol... 

Sapozhnikov and Markovskii measured at 298.15 K the enthalpy of dissolution of a number of zinc, cadmium, and mercury selenites in mineral aeid in a calorimeter. Sulphuric acid (aq, 1 50) was used for the zinc and cadmium compounds, while hydrochloric acid (aq, 1 35) was used for the mercury salts. The experimental details are few and... 

Problem Unfortunately, the reactions of acidic and basic solutions are not spectacular colorless solutions result again in colorless salt solutions. In order to show, at least, through temperature measurements, that an exothermic reaction of hydronium ions and hydroxide ions exists, same amounts of 2M solutions of hydrochloric acid and sodium hydroxide solution are used a temperature increase of approximately 13°C can be shown a neutralization enthalpy of 57kJ/mol will be calculated. If one chooses arbitrary pairs of strong acids and bases of the same concentration, then it can be seen that the temperature is always the same it does not depend on the spectator ions , but only on concentrations of H30 + (aq) and OH (aq) ions. 

The standard enthalpy of formation of lithium nitride has been determined by solution calorimetry. The enthalpies of reaction of LigN with water and hydrochloric acid are -581.62 1.42 and -803.50 1.26kJmoL, respectively. These values are combined with auxiliary thermochemical data to derive a weighted mean value of -164.93 1.09 kJ moP for the standard enthalpy of formation of lithium nitride. This value differs by about 8 kcal moP from previous determinations.Lithium nitride reacts in the solid state with M (M = Ca, Th, or Hf) to form MN as intermediate, and with MN to form Li2MN2. These reactions have been studied using d.t.a.and t.g.a. X-ray powder diffraction investigation shows... 

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