Enthalpy Essay

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ENTHALPY What is enthalpy? Enthalpy is the amount of heat content used or released in a system at persistent pressure. Enthalpy is typically articulated as the change in enthalpy. The change in enthalpy is linked to a change in internal energy (U) and a change in the volume (V), which is multiplied by the constant pressure of the system. 23/04/14 (http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/State_Functions/Enthalpy) When the reaction is giving off heat, it is exothermic. In this case, the enthalpy change is negative, since the reaction is going from high energy to low energy due to the loss of heat energy to its surroundings. If energy flows from the surrounding environment and heat is being taken in, it is endothermic. The change is positive as the system is gaining energy in the form of heat. Bond Making and Bond Enthalpy Bond enthalpy is the energy that is required to break a chemical bond. In most cases it is expressed in units of kJ mol-1, measured at 298 K. The most accurate/exact bond enthalpy of a particular chemical on is all dependant on the molecular environment in which the bond exists. The molar bond enthalpy is the energy required to break one mole of bonds between pairs of atoms in the 'gaseous molecule'. Bond enthalpy values are usually expressed in kJ mol-1 of bonds broken. 21/04/14 (http://www.avogadro.co.uk/h_and_s/bondenthalpy/bondenthalpy.htm) Bond making is an exothermic process. However if a certain bond in a molecule is broken and then reformed, then the same amount of energy must be involved. During a chemical reaction bonds in the reactants are broken and new bonds are made in the products. Find H for the following reaction given... ... middle of paper ... ...n -Caution with any glass items Disposal of residues -Extra liquids Colorimetry Colorimetry is the process of determining the concentration of a substance of a substance by measuring the relative of light. The instrument used is called a calorimeter. Colorimetry is the scientific method that is used to classify the colours of the spectrum. (http://www.docbrown.info/page07/appendixtrans09.htm) Background knowledge In chemistry, Colorimetry is used a lot. They use it for things such as colour painting, food manufacturing, and textiles. Colorimetry can also be used to measure light. The amount of light absorbed is called and also is measured as the absorbance which is a use of the coloured solute concentration. To use a colorimeter, different kinds of solutions have to be made, this includes a regulator or orientation of identified concentration.

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