Exp 14

Exp. 14:  Calorimetry and Hesss Law Purpose: This experiment employs calorimetry to determine enthalpy changes for cardinal replys that safe(p) deal conveniently be performed in the laboratory. and so it makes use of Hesss Law to calculate the enthalpy change for a reception which is not at a time observed. Introduction: An exothermic response releases altering system, and that fondness head for the hillss into the surroundings and is usually observed as a temperature growth in the solvent. container, and other immediate surroundings. An insulated container called a bomb calorimeter can be used to limit the heat flow with good accuracy to the solvent and bomb. Thus -q reaction = qsolution + qbomb -- Eqn. 1 where q is the symbol for heat flow which impart be measured in Joules. The negative sign on the left of the par says that heat is flowing out of the reaction; so the heat flow out of the reaction is embody to the heat flow into the solution and the calorimeter. It is very important to recall that whenever heat is flowing out of a cognitive content or reaction the value of q forget be negative. In the slip of our experiment, the calorimeter absorbs so little heat that qbomb is nearly zero and and then the equivalence simplifies to -qreaction = qsolution -- Eqn.

2 The temperature change caused by the addition of a presumption amount of heat will depend on the check heat, Csp, of the substance. The specific heat of water (and a good stem for dilute aqueous solutions) is 4.184 J/g oC. Thus, the heat friendship can be metric by the equation q = (Csp)(m)(?T) -- Eqn. 3 The mass of the sub! stance is m, and the change in temperature is ?T. Change in temperature is always calculated as (final temperature) - (initial temperature). Our experiment is run at constant pressure, therefore the heat changes observed will be equal to the enthalpies of reaction, (?Hrxn for the reactions considered. We will obtain experimental data to directly calculate the (?Hrxn for two reactions in this experiment. The enthalpies of...If you want to get a full essay, rank it on our website: BestEssayCheap.com

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