1 Introduction The Heat of Reaction, also known and Enthalpy of Reaction is the change in the enthalpy of a chemical reaction that occurs at a constant pressure. It is a thermodynamic unit of measurement useful for calculating the amount of energy per mole either released or produced in a reaction. Since enthalpy is derived from pressure, volume, and internal energy, all of which are state functions, enthalpy is also a state function. As it is a form of energy, heat plays multiple important roles in chemical reactions The reaction heat of CL-20/HMX Cocrystal (Q) was determined at 293.15, 298.15, 303.15, 308.18 and 313.15K by using a DC-08 Calvet microcalorimeter to obtain fundamental thermodynamics parameters.
1 Experiment Section
1.2 Reagents: CL-20/HMX Cocrystal was prepared and purified in our laboratory (see
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From Eq.(1), the empirical formula of enthalpy[15] ∆_diss H(b=b)of dissolution in DMF and the value of the standard enthalpy of dissolution ∆_diss H(b=0)
For CL-20/HMX Cocrystal are as follows:
∆_diss H=12.78509-1480.31579b+579.5614b^(1⁄2) (4.2)
And
∆_diss H_m^θ=12.78509 kJ 〖mol〗^(-1) (4.3)
According to the relationship as shown in Eq.(4.4):
∆_diss H_apparent=∆_diss H(b=b)-∆_diss H(b=0) (4.4)
From Eq.(4.1), the empirical formula of relative apparent molar enthalpy ∆_diss H_apparent for CL-20/HMX Cocrystal is obtained:
∆_diss H_apparent=-1480.31579b+579.5614b^(1⁄2) (4.5)
According to the empirical formula as presented in Eq(4.6):
∆_diss H_partial=b((∂∆_diss H)/∂b)+∆_diss H_apparent (4.6)
Form Eqs.(1) and (2), the following empirical formula of the relative partial molar enthalpy for CL-20/HMX Cocrystal is obtained:
∆_diss H_partial=-2960.63158b+869.3421b^(1⁄2) (4.7)
According to the empirical formula described in
This is by using the same mass and realizing that the specific heat of both the regular water and the hot water are the same. In our procedure, 100 mL of hot water was mixed with 100 mL of the regular water; therefore, the masses in Equation 3 cancel out (the densities of the water at different temperatures aren’t exactly the same, but the difference is negligible). This leads to the change in temperature of the hot water equaling the negative change of temperature in the regular water, shown as:
Physical Chemistry Laboratory Manual, Physical Chemistry Laboratory, Department of Chemistry, University of Kentucky, Spring 2006.
== = Hess’s law of heat summation states that the value of DH for a reaction is the same whether it occurs directly or as a series of steps. This principle was used to determine the change in enthalpy for a highly exothermic reaction, the combustion of magnesium metal. Enthalpy changes for the reactions of Mg in HCl (aq) and MgO (s) in HCl (aq) were determined experimentally, then added to that for the combustion of hydrogen gas to arrive at a value of –587 kJ/mol Mg.
Specific heat capacity of aqueous solution (taken as water = 4.18 J.g-1.K-1). T = Temperature change (oK). We can thus determine the enthalpy changes of reaction 1 and reaction 2 using the mean (14) of the data obtained. Reaction 1: H = 50 x 4.18 x -2.12.
The Enthalpy Change of Different Alcohols My aim is to compare the enthalpy change of combustion of different alcohols in relation to the structure of each molecule. The enthalpy change of combustion of a fuel is a measure of the energy transferred when one mole of the fuel burns completely. In a chemical reaction, bonds must either be made or broken, this involves an enthalpy change. The formation of bonds is exothermic, energy is lost to the surrounding; on the other hand, breaking bonds is endothermic, energy is taken in. I obtain the value for the enthalpy change of each fuel by using the formula: Energy transferred from the fuel=
The molar specific heats of most solids at room temperature and above are nearly constant, in agreement with the Law of Dulong and Petit. At lower temperatures the specific heats drop as quantum processes become significant. The Einstein-Debye model of specific heat describes the low temperature behavior.
The objective of this experiment was to identify a metal based on its specific heat using calorimetry. The unknown metals specific heat was measured in two different settings, room temperature water and cold water. Using two different temperatures of water would prove that the specific heat remained constant. The heated metal was placed into the two different water temperatures during two separate trials, and then the measurements were recorded. Through the measurements taken and plugged into the equation, two specific heats were found. Taking the two specific heats and averaging them, it was then that
The first law of thermodynamics simply states that heat is a form of energy and heat energy cannot be created nor destroyed. In this lab we were measuring the change in temperature and how it affected the enthalpy of the reaction.
be yes as I will then be able to use enthalpy change of reaction to
Aim- To determine the enthalpy change for the reaction of between cooper sulphate and zinc.
Thickett, Geoffrey. Chemistry 2: HSC course. N/A ed. Vol. 1. Milton: John Wiley & Sons Australia, 2006. 94-108. 1 vols. Print.
Thermodynamics is the branch of science concerned with the nature of heat and its conversion to any form of energy. In thermodynamics, both the thermodynamic system and its environment are considered. A thermodynamic system, in general, is defined by its volume, pressure, temperature, and chemical make-up. In general, the environment will contain heat sources with unlimited heat capacity, allowing it to give and receive heat without changing its temperature. Whenever the conditions change, the thermodynamic system will respond by changing its state; the temperature, volume, pressure, or chemical make-up will adjust accordingly in order to reach its original state of equilibrium.
Heat is thermal energy being transferred from one place to another, because of temperature changes. This can take place by three processes. These three processes are known as conduction, convection, and radiation.
As discussed in class, submission of your solutions to this exam will indicate that you have not communicated with others concerning this exam. You may use reference texts and other information at your disposal. Do all problems separately on clean white standard 8.5” X 11” photocopier paper (no notebook paper or scratch paper). Write on only one side of the paper (I don’t do double sided). Staple the entire solution set in the upper left hand corner (no binders or clips). Don’t turn in pages where you have scratched out or erased excessively, re-write the pages cleanly and neatly. All problems are equally weighted. Assume we are working with “normal” pressures and temperatures with ideal gases unless noted otherwise. Make sure you list all assumptions that you use (symmetry, isotropy, binomial expansion, etc.).
Plontke, R. (2003, March 13). Chemnitz UT. TU Chemnitz: - Technische Universität Chemnitz. Retrieved April 1, 2014, from http://www.tu-chemnitz.de/en/