ENTHALPY OF NEUTRALIZATION AND HESS LAw Balanced Reaction Equations (3 of these:
ID: 693302 • Letter: E
Question
ENTHALPY OF NEUTRALIZATION AND HESS LAw Balanced Reaction Equations (3 of these: Data: 1. Concentration of HCI 2.COM ation 5M 3. Concentration of NH,20M 4 2. Concentration of NaOH d. Concentration of NHLCI2.O0M Reaction 1 Reaction 2 Reaction 3 4a.I Volume of acid (mL) Volume of base (mL) Total volume (mL) 49.7 50.6 ao. 090 163 25.2 Mass of total solution. (e) (2 Final temp. C) Initial temp. C) AT (C) heat, q J) AH (kj/mol) 24.314. (0401 74.05 004.3 p.O1 Observations: record any and all relevait observations: Reagent Table add addirional lines if needed Formula Appearance and notes or b Name Am mnia Solution NH3 cobExplanation / Answer
5. H = (q/moles of reactant)/1000 (in kJ / mol)
For reaction 3
From Experimental
Moles of acid moles of base = 2*49.9/1000
= 0.0998
H = 4654.3 /0.0998
46636.2 J =46.636 kJ
The reaction is exothermic so the value will be negative
From Hess law
H (For reaction 3) = H (reaction 1) - H (for reaction 2)
= - 65.188 – (-4.634) [H (reaction 1) and H (for reaction 2) are calculated in same manner as for reaction 3]
= -60.554 kJ/mol
Experimental H for reaction 3
Calculated experimental H using Hess law for reaction 3
Theoretical
H (kJ/mol)
-46.636
-60.554
-57.9
6. The experimental value is quite different from the Hess law calculated value.
= -60.554 – (-46.636)/ -60.554 * 100
= 22.98 %
This experimental value is not within the agreement.
7. The value of experiment (-46.636 kJ/mol) is even different from theoretical value (-57.9 kJ/mol)
Which suggests the failure of this technique to be used for calculation of H.
= -57.9 – (-46.636)/ -57.9 *100
= 19.5 %
8. The errors during measurements of the reactions temperature, weight of the substance, volume, time etc could be improved to make this technique more accurate in the calculation of H. For example, the thermal thermometer, the burette and the scale which was used are not entirely precise, so one way of getting a more accurate result would be using more precise equipment to measure different aspects of the reactions. And the experiment should be repeated at least twice to minimize the human error.
Experimental H for reaction 3
Calculated experimental H using Hess law for reaction 3
Theoretical
H (kJ/mol)
-46.636
-60.554
-57.9
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.