Calorimetry

Heat of Neutralization

Concepts

Large concentrations of hydrogen ion and hydroxide ion cannot coexist in solution, because the neutralization reaction

H⁺ (aq) + OH^- (aq)

H₂O (l)

strongly favors the product (water).

In this experiment, an aqueous hydrochloric acid solution will be added to an aqueous sodium hydroxide solution. The neutralization reaction will occur until either H⁺ or OH^- is entirely consumed. The reactant which is consumed first is called the limiting reactant.

The molar enthalpy of neutralization is defined as

ΔH_neut =

q_neut

n

where q_neut is the heat of neutralization, measured calorimetrically, and n is the moles of the limiting reactant.

Experiment

Objective:

Determine the molar enthalpy of neutralization.

Approach:

Add a known volume of 3.00 M aqueous HCl to a known volume of 1.00 M aqueous NaOH.
Observe the temperature of the system before and after the neutralization reaction occurs.
Calculate the change in temperature for the system.
Use the temperature change and heat capacities for the calorimeter and aqueous solution to calculate the heat of neutralization.
Divide the heat of neutralization by the moles of the limiting reactant to determine the molar enthalpy of neutralization.

Part 1

In this part of the experiment, the calorimeter is filled with 50.0 mL of 1.00 M aqueous NaOH.
The reservoir contains 20.0 mL of 3.00 M aqueous HCl. Both solutions start at the same initial temperature.

The heat capacity of the calorimeter (C_cal) is 78.2 J ^oC^-1.

The specific heat capacity of the aqueous solutions is 4.184 J ^oC^-1 g^-1.

Part 2

The conditions in this part of the experiment are the same as those in Part 1.

The upper reservoir contains 3.00 M aqueous HCl and the calorimeter initially contains 1.00 M aqueous NaOH. Both solutions start at the same initial temperature.

The heat capacity of the calorimeter (C_cal) is 78.2 J ^oC^-1.

The specific heat capacity of the aqueous solutions is 4.184 J ^oC^-1 g^-1.

Repeat the experiment using various volumes of HCl and NaOH. You should get the same molar enthalpy of neutralization.

Heat of Solution of Ammonium Nitrate Heat of Solution of Sulfuric Acid

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