Investigation 18C
Calorimetry: Heat of Neutralization
Student Name: __________________________
Date: ________________________________
A1
D
A2
A3
-
-
-
A1
DCP
A2
A3
A1
-
N/A
A3
-
N/A
Theory
In nearly all chemical and physical changes occurring in nature, heat (energy) is
either evolved or absorbed. In the laboratory a calorimeter is used to measure the
heat flow for a chemical reaction. Reactions which evolve heat are exothermic and
have negative H values. Reactions which absorb heat are endothermic and have
positive H values.
In this experiment you will use the technique of calorimetry to determine the heat of
neutralization of a strong acid with a strong base. The heat of neutralization, Hn, is
computed by (a) assuming the density and specific heats of the acidic and basic
solutions are the same as water’s, and (b) measuring the temperature change when
the two are mixed.
Hn = - specific heat (H2O) x mass (acid solution + base solution) x T(H2O)
n (limiting acid or base)
Purpose
To determine the quantity of heat evolved in the neutralization of a strong acid with a
strong base.
Materials
100 mL graduated cylinder (2)
calorimeter
thermometer (-10 to 110 0C)
safety goggles
CE
A2
stopwatch
1.0 mol/dm3 NaOH
1.2 mol/dm3 HCl
Safety
Acids and bases are caustic, handle with care. Clean up spills immediately.
N/A
Procedure and Observations
1. Using a graduated cylinder, add 50.0 mL (0.1 mL) of a standard 1.0 mol/dm3
(0.1 mol/dm3) NaOH solution into a clean, dry calorimeter. Record the NaOH
solution’s temperature (0.2 C) by inserting a thermometer into the lid so that
the bulb is below the surface of the solution.
2. Using a graduated cylinder, add 50.0 mL (0.1 mL) of a 1.2 mol/dm3 (0.1
mol/dm3) of HCl solution into a clean, graduated cylinder. Record the HCl
solution’s temperature (0.2 C).
3. Carefully and quickly add the acid to the base, replace the lid + thermometer and
swirl gently. Do not use the thermometer as a stirring rod.
4. Measure and record the temperature (0.2 C) as a function of time. Plot on
linear graph paper, temperature vs time to determine the maximum temperature
change. Have your instructor approve your graph and the T you have
determined before continuing with the remaining calculations and conclusions.
Conclusions and Evaluation
Include in your conclusions the net ionic equation and the enthalpy value for this net
reaction. Compare your value to the accepted value. Discuss relevant sources of
error.