Heat of Neutralization in a Calorimeter with Weak and Strong Electrolytes

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Heat of Neutralization in a Calorimeter with Weak and Strong Electrolytes

Erin

Lab Performed: November 11th, 2008

Section 006

T.A:  Teresa


Introduction

The purpose of this experiment is to find the concentration of the unknown HCl as a strong electrolyte to observe the enthalpy changes between strong and weak electrolytes. This is conducted by using a “coffee-cup” calorimeter and a series of solutions: HCl, HNO3, NaOH (all strong electrolytes) and Phenol (weak electrolyte).

Both strong electrolytes and weak electrolytes are used in this lab. The difference between strong electrolytes and weak electrolytes is that strong electrolytes completely ionize in aqueous solution making the solution a good conductor. In contrast, weak electrolytes do not behave the same way and will only partially ionize, but is only a fairly good conductor of electricity (Petrucci et al, 2007).  The examples of strong electrolytes in this experiment are HCl, HNO3 and NaOH. The phenol solution that it is use is a weak electrolyte.

The reaction is happening within a “coffee-cup” or Styrofoam cup calorimeter where the neutralization reaction between the NaOH and the acid will act as the system. The heat that is absorbed or released by the system during the reaction within the calorimeter, is called the heat of the reaction, q. The formula for q is: q = mcΔt

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The heat of the system is comes from the combination of hydrogen ions and hydroxide ions to make water. When the H+ (hydrogen ions) and OH- (hydroxide ions) ions come from two strong electrolytes, they will have no effect on the heat of neutralization, but it is found that reactions with strong electrolytes produce the same amount of heat (-55.90KJ/mol). Likewise, within a reaction with a weak electrolyte, such as phenol, the nature of the solution will determine the heat of the reaction – either smaller or larger than -55.90KJ/mol of H+ (Strathopulous, 2008).

Materials and Methods

        The experimental procedure ...

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