The calorimeter above was used to determine the enthalpy of the reaction between hydrochloric acid and sodium hydroxide. The relevant temperatures at the time of reaction (assuming the reaction was instantaneous) were determined as above. Temperatures were recorded as a function of time and extrapolated to the time of mixing. The generic graph is shown below. The temperature axis is again intentionally not displayed. The relevant information is given in the table below.
The data for the reaction between HCl and NaOH were as follows:
Value
Units
Concentration of HCl
2.45
M
Volume of HCl
50.0
mL
Density of HCl
1.02
g/mL
Concentration of NaOH
2.39
M
Volume of NaOH
55.0
mL
Density of NaOH
1.02
g/mL
Specific Heat of HCl & & NaOH & Reaction Mixture
3.97
J/g-K
Temperature of HCl at 3.0 min, Tacid (from graph)
25.4
oC
Temperature of NaOH at 3.0 min, Tbase (from graph)
25
oC
Temperature of reaction mixture at 3.0 min, Tmix (from graph)
40.7
oC
If the temperatures of the acid and base at the time of mixing are different, use their average as the temperature of the mixture before reaction. Use the average also as the initial temperature of the calorimeter.
What is the weight of the reaction solution in grams?
107.1 Correct
the change in temperature experienced by the reaction mixture (and the calorimeter) extrapolated back to the time of mixing?
15.5 Correct
What is the molar enthalpy, ÎHneut, of the reaction in:
H+ (aq) + OH- (aq) â H2O (l)
in kJ/mol?
-57.3
Question:
The above experiment is repeated using the weak monoprotic acid, crotonic acid, in place of hydrochloric acid. The molar enthalpy of the reaction between the crotonic acid and sodium hydroxide, ÎHweak is determined to be -51.3 kJ/mol. Using Hess' Law and your result for HCl, what is the enthalpy of dissociation of crotonic acid in kJ/mol?
Temperature vs Time Mixture BASE baoc acid Acid 0.0 0.5 10 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.07.5 8.0 8.59.0 9.5 10.0 Time (min)
