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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

H1HR1  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.