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To determine enthalpy change of hydration of magnesium sulphate(VI)

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Introduction

Chemistry Lab report 1) Experiment No: 8A 2) Objective: To determine the heat of formation of calcium carbonate. 3) Date: 26th Nov, 2010 4) Theory: The experiment consists of 2 parts: a) In the 1st part, an accurately weighed known mass of calcium is added to a given dilute hydrochloric acid. During the addition, the following occurs: Ca(s) + 2H+(aq) --> Ca2+(aq) + H2(g) With the help of the data of heat change of the solution mixture, the average heat evolved by one mole of calcium during the reaction can be calculated. b) In the 2nd part, an accurately weighed known mass of calcium carbonate is added to a given dilute hydrochloric acid. During the addition, the following occurs: CaCO3(s) ...read more.

Middle

Calculation: Note: No temperature drop can be observed after the max temperature is attained for 4 readings. Note: No temperature drop can be observed after the max temperature is attained for 4 readings. Extrapolation procedure cannot be done. Therefore, the temperature change of 1st part exp. = 28-25 = +3oC the temperature change of 2nd part exp.= 26-25 = +1oC Heat evolved in 1st part : =(mc T) x (no. of mol)-1 =(100 x 4.2 x 3) x (0.53 / 40.1)-1 =-95332 J mol-1 Heat evolved in 2nd part: =(mc T) x (no. of mol)-1 =(100 x 4.2 x 1) x (1/100.1)-1 = -42042 J mol-1 Using enthalpy cycle: Ca(s) + C(graphite) +3/2O2(g) CaCO3(s) Ca2+(aq) + H2(g) ...read more.

Conclusion

It' depends on the standard enthalpy change of a reaction is independent of the route by which the chemical reaction takes place, which only depends on the difference between the standard enthalpies of reactants and products, i.e. conservation of energy. 3. Why is this law useful? This principle is useful as the standard enthalpy change of some reaction might not be able to find directly, and thus Hess's law can be used and the standard the enthalpy change of the reaction can be calculated indirectly by this method. 4. Discuss the possible sources of errors. State how to minimize the possible errors. A. The solid labeled "calcium" is suspected to be calcium oxide, which show white color but not grey shinny color. B. Heat produced the reaction might heat up the air inside the beaker, which cannot be avoided. C. Error in reading thermometer D. Error in weighing ?? ?? ?? ?? ...read more.

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