Heats of formation kJ mole

Temperature, °C Heat of formation, kJ/mole Density, kg/m at 20°C Heat capacity, J/moleK Heat of melting, kJ/mole... 

Oxidizer Available oxygen Melting point, °C Density, g/cm Heat of formation, kj / mof Heat capacity, J/(mol-K) Gas, moles per 100 g"... 

Equations (1) and (2) are the heats of formation of carbon dioxide and water respectively Equation (3) is the reverse of the combustion of methane and so the heat of reaction is equal to the heat of combustion but opposite in sign The molar heat of formation of a substance is the enthalpy change for formation of one mole of the substance from the elements For methane AH = —75 kJ/mol... 

Ammonium fluoride is a white, deflquescent, crystalline salt. It tends to lose ammonia gas to revert to the more stable ammonium bifluoride. Its solubiUty in water is 45.3 g/100 g of H2O at 25°C and its heat of formation is —466.9 kJ/mol ( — 116 kcal/mol). Ammonium fluoride is available principally as a laboratory reagent. If it is needed in large quantities, one mole of aqueous ammonia can be mixed with one mole of the more readily available ammonium bifluoride (1). 

Specific Heat (Cp) 32.7 J/mole K Heat of Formation (-AaHj) at 298K (KJ/g-atom metal) (1) 23.0... 

C06-0093. Solid urea, (NH2)2 CO, bums to give CO2, N2, and liquid H2 O. Its heat of combustion is -632.2 kJ/mol. (a) Write the balanced combustion equation, (b) Calculate the heat generated per mole of H2 O formed, (c) Using this heat of combustion and the appropriate thermod3uamic data, determine the heat of formation of urea. 

Table 2.2 Heat of formation Ahf in kJ/mole (at 25 °C and 1 atm)a (abstracted from Reference [2])...

Determine by calculation the enthalpy of formation in kJ/mole of CH4 given that its heat of combustion is 50.0 kJ/g at 25 °C. The heat of formation for carbon dioxide is -394 kJ/mole and water vapor is -242 kJ/mole. 

Other properties Heat of formation of nylon = —135 kJ/mole... 

The heat of combustion of nylon is 30.8 kJ/g. Find the heat of formation of the nylon in kJ/mole. 

Use the information in the chapter 2 to work the problem. You can assume constant specific heats of the species at an appropriate mean temperature (use 1600 K). Also, the heat of formation of polystyrene is - 38.4 kJ/mole. 

Propellant chemists have proposed a new high energy liquid oxidizer, penta-oxygen 05, which is also a monopropellant. Calculate the monopropellant decomposition temperature at a chamber pressure of 10 atm if it assumed the only products are O atoms and 02 molecules. The heat of formation of the new oxidizer is estimated to be very high, +1025 kJ/mol. Obviously, the amounts of 02 and O must be calculated for one mole of 05 decomposing. The 05 enters the system at 298 K. Hint The answer will lie somewhere between 4000 and 5000 K. 

Many years later, Swihart and Carr (J. Phys. Chem. 101,7434,1997) published heats of formation for two of the species H3SiSiH2Cl AHJ = —89.1 and H3SiSiHCl2 AHj = -268.6 kJ/mole. How do your estimates compare with these calculated results ... 

We can calculate just how much heat is released when plaster is mixed with water using a concept called heat of reaction. Symbolized AH, it is derived from the heat of formation, AHf, of the reactants and products in a chemical change. Heats of formation values (AHf), are compiled on special thermodynamic tables and expressed using the unit kilojoules per mole (kj/mole). The heats of formation of plaster of Paris, gypsum, and water are -1575.2 kj/mole, -2021.1 kj/mole, and -285.8 kj/mole, respectively. To find the heat of the reaction, it is necessary to subtract the heat of formation of the reactants from the heat of formation of the products ... 

In the first reaction, 393.51 kJ are liberated (exothermic reaction) when 1 mol of gaseous C02 is formed from graphite and oxygen. When 2 mol HI are formed from gaseous hydrogen and solid iodine, there are 52.72 kJ absorbed (endothermic reaction). In the case of the second reaction, the standard heat of formation is +26.36 kJ/mol HI formed the total amount of energy involved in the reaction as written is twice the standard heat of formation because there were two moles of product formed. The reason why AH is the symbol instead of AHf is that the reaction does not address the formation of one mole of product therefore, AHf, which is calculated on a per-mole basis, is not an appropriate symbol for the reaction. Further, notice that the 0 is used in AHj and with other factors (S°, AGp or AE°) to indicate the standard condition of pressure, 1 atm (1 bar), usually 25°C and, for dissolved substances, of concentration 1 molal (refer to Chapter 12). For easy reference, selected standard heats of formation for selected substances are located in Table 7-1 however, notice that there are no elements listed in the table. 

The standard formation enthalpy for water is equal to 286 kj/mole H2 relative to the formation of liquid water and corresponding to (HHV) of H2. The theoretical voltage for pure water decomposition is 1.23 V. However, the majority of conventional electrolysis devices need at least 2.0 V when economically reasonable current densities are maintained. This value translates into a water electrolysis Faraday s efficiency of about 74%. If a thermal-to-electric conversion efficiency of 45% is assumed, the total equivalent heat requirement corresponds to a heat input of 859 kj/mole H2. 

The heats of formation of H2S04(1) and NaOH(c) are given in Table B.l, and the heats of solution of these species are given in Table B.ll. Perry s Chemical Engineers Handbook (see footnote 1) on p. 2-193 gives the standard heat of formation of NaiSOrfaq. r = 1100) as -330.82 kcal/mol Na2S04 = —1384 kJ/mol Na2 04. In the absence of heat of solution data, we will assume that this value also applies to the solution for which r = 69 moles of water per mole of solute. The standard heats of formation of the species involved in the reaction... 

Note that the heat of formation of HF is multiplied by 2 because two moles of HF are formed. Also note that it is not necessary to change the sign of A// (H2S) and that A77j (F2) is 0.0 kJ because the standard heat of formation of an element in its standard state is zero. 

We first describe the standard heat of formation (AH/) and then the standard heat of combustion (AH ). The units of both quantities are usually tabulated as energy per mole, such as J/g mol, kJ/g mol, kcal/g mol, or Btu/lb mol. The per mole refers to the specified reference substance in the related stoichiometric equation. 

Next we calculate the standard heat of reaction. The moles of FeS2 that react are 0.7083—0.0242 = 0.684 kg mol. Oxygen and nitrogen have zero values for AH and the gangue does not react. We will use the following tabulated heats of formation (in kJ/g mol) to calculate... 

Aluminum powder is frequently added to explosives and propellants to improve their performance. The addition of aluminium results in considerable gain in heat of explosion because of the high heat of formation of aluminia (1658 kJ/mole, 16260 kJ/kg) leading to higher temperatures of the fumes. Aluminium not reacted in the detonation front might be oxidized atmospheric oxygen to induce post-heating in the fume zone and to increase the -> air blast or even to initiate a delayed secondary explosion. 

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