InterviewSolution
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InterviewSolution
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When 100 mL of 1.0 M HCl was mixed 100 mL of 1.0 M NaOH in an insulated beaker at constant pressure, a temperature increase 5.7^(@)C was measured for the beaker and its contents (Expt. 1). Because the enthalpy of neutralization of a strong acid with a strong base is a constant (-57.0 kJmol^(-1)), this experiment could be used to measure the calorimeter constant. In a second experiment (Expt.2) 100 mL of 2.0 M acetic acid (K_(a)=2.0xx10^(-5)) was mixed with 100 mL of 1.0 M NaOH (under indentical conditions to Expt. 1) where a temperature rise of 5.6^(@)C was measured (Consider heat capacity of all solutions as 4.2 Jg^(-1)K^(-1) and density of al solutions as 1.0 gmL^(-1))Enthalpy of dissociation (in KJmol^(-1))of acetic acid obtained from the Expt.2 is |
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Answer» `1.0` Mass of aqueous content in expt. `1=(100+100)xx1=200g` implies Total heat capacity = `(C+200xx4.2)J//K` Moles of acid, base neutralised in expt. `1=0.1xx1=0.1` implies Heat released in expt. `1=0.1xx57=5.7 KJ` `implies5.7xx1000=(C+200xx4.2)xxDeltaT` `5.7xx1000=(C+200xx4.2)xx5.7` `implies (C+200xx4.2)=1000` In second experiment, `n_(CH_(3)COOH)=0.2, n_(NAOH)=0.1` Total mass of aqueous content = 200 g implies Total heat capacity = (C+200`xx`4.2)=1000 implies Heat released = `1000xx5.6=5600 J` Overall, only 0.1 mol of `CH_(3)COOH` undergo neutralization `implies DeltaH_("neutralization")" of "CH_(3)COOH=(-5600)/(0.1)` `=-56000 J//mol=-56 KJ//mol` `impliesDeltaH_("IONIZATION")" of "CH_(3)COOH=57-56=1KJ//mol` |
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