Question

A Study in Spontaneity

Data and Analysis

100.00 mL distilled water

Calculated mass of KNO3 from prelab = 10.1
Part I KNO3

Mass of KNO3 Run1 = 10.1 | Run2 = 10.1
Initial temperature (Ti) Run1 = 21.8 | Run2 = 21.8
Final temperature (Tf) Run1 = 14.5 | Run2 = 14.5

Calculate qsystem (J) =
Calculate moles of KNO3 (mol) =

Calculate ΔH (kJ/mol) =
Average ΔH (kJ/mol) =

Use ΔH – TΔS < 0 to calculate the entropy. Calculated ΔS =

Calculated mass of KOH from prelab = 5.6
Part II KOH

Mass of KOH Run1 = 5.6 | Run2 = 5.6
Initial temperature (Ti) Run1 = 22 | Run2 = 29
Final temperature (Tf)Run1 = 28.6 | Run2 = 35.1

Calculate qsystem (J)
Calculate moles of KOH (mol) =

Calculate ΔH (kJ/mol) =

Average ΔH (kJ/mol) =

Use ΔH – TΔS < 0 to calculate the entropy. =

Calculated ΔS =

Answer 1

Calculate enthapy

Calculate q(system) = 100 x 4.184 x (14.5 - 21.8) = 3054.32 J

moles KNO3 = 10.1/101.1032 = 0.10 mol

dH = 3054.32/0.1 x 1000 = 30.5432 kJ/mol

To calculate entropy

q(system) = 100 x 4.184 x (28.6 - 22) = 2761.44 J [Run 1]

q(system) = 100 x 4.184 x (35.1 - 29) = 2552.24 J [Run 2]

dH = 2761.44 x 56.1056/5.6 = 27.67 kJ/mol

dH = 2552.24 x 56.1056/5.6 = 25.57 kJ/mol

Average dH = 26.62 kJ/mol

Average final temperature = (28.6 + 35.1)/2 = 31.85 oC = 304.85 K

dS = 26.62/304.85 = 87.322 J/K.mol