Page 36
ΔHR1= R1=-1.875kJ875 kJ
ΔHR2= R2=-4.678kJ678 kJ
ΔHR3= R3=-2.865kJ865 kJ
mol R1=R1=2.00/(22.99+16.00+1.008)= 0.05 mol
mol R2=R2=2.00/(22.99+16.00+1.008)= 0.05 mol
mol R3=R3=1.0*50.1000= 0.05 mol
ΔH/mol R1=R1=-1.875/0.05= -37.5 kJ/mol
ΔH/mol R2=R2=-4.678/0.05= -93.6 kJ/mol
ΔH/mol R3=R3=-2.865/0.05= -57.3 kJ/mol
-ΔH1HR1 ΔH2HR2 ΔH3HR3
-37.5+-57.3= -94.8 kJ/mol
37.5+-93.6= -56.1 kJ/mol
|-94.8+93.6| / |-93.6| *100= 1.28% error
Conclusion:
The purpose of the lab was to practice applying Hess's Law and verifying that the heat of a reaction is equal to the sum of the other reactions. We achieved this by using a coffee cup calorimeter to combine NaOH with water and HCl and using a thermal probe to measure the initial and final temperature, which was used along with the mass or volume of NaOH, to find the heat released, which was used to find ΔH. We then used the mass of NaOH to find the ΔH/mol. We then added two reactions and compared them against the third to verify the data/calculations.