• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Heat of Neutralization in a Calorimeter with Weak and Strong Electrolytes

Free essay example:

Heat of Neutralization in a Calorimeter with Weak and Strong Electrolytes


Lab Performed: November 11th, 2008

Section 006

T.A:  Teresa


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

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 used for this experiment was outlined in the CHEM 120L lab manual, Experiment 4. All steps were followed without deviation.


Table 1: Observation of Acids and Bases


Concentration of Solution Used

 Acid            Base

ΔT from graph


Moles of H2O Formed (nwater)

Number of kJ/mole of H2O formed


















































Since the number of KJ/mol of water formed will be the same as the KJ/mol as the electrolyte. Seeing as these acids or electrolytes should all be strong, except for phenol, these values are fairly accurate. This is known because the correct because the amount of heat that is given off, theoretically by strong electrolytes is 55.90KJ/mol. The values that were found are all technically negative values because the process is exothermic, meaning that the heat moves from the system, neutralization, to the surroundings.

 The calculations show that the neutralization reaction with NaOH and HNO3 produces an average molar enthalpy of 54 kJ/mol. Both HNO3 and NaOH are strong electrolytes and therefore both completely ionize in water. Of the four parts conducted in this experiment, this was the closest value to the number of kilojoules per mole of water formed.

To solve for the molarity of the unknown hydrochloric acid, the average of the heat of reactions from both trials of part A were used. By finding the moles of water (which is equal to the amount of moles of HCl) the molar enthalpy was determined using q = mcΔt. By taking the average molar enthalpy, -53KJ/mol, the moles of the unknown HCl can be determined. The average morality of HCl unknown #5 that was found was 2.24M. The calculations are shown in the results section as part D.

With an average molar enthalpy of 54 kJ/mol, the neutralization reaction between HNO3 and NaOH produced the most heat per mole of H2O formed. This reemphasizes on the point that strong electrolytes dissociate completely as well as releases more heat for the reaction. If compared to part c, neutralization reaction between phenol and sodium hydroxide (a weak electrolyte), it is apparent that the reaction with the strong electrolytes produces more heat; average heat of reaction for part C equalled 40 kJ/mol versus the heat of reaction for part B which was 54 kJ/mol. The solutions in part C do not completely ionize which is a result of the lower molar enthalpy. These results should have shown more of a difference in heat, however there are many sources of error so these results are slightly off.


In this experiment, the strong acids that were used were HCl and HNO3 – strong electrolytes. The weak acid that was used was called phenol – weak electrolytes. The base that was used for all 4 neutralization reactions was a strong base called sodium hydroxide which also happens to be a strong electrolyte.

        Because there were so many trials and required readings, there was plenty of room for error in this lab. Some sources of error include reading errors such as reading the thermometer incorrectly and not keeping the readings constant (i.e. every 10 seconds, every 5 seconds), keeping time inconsistently. When placing the thermometer in the calorimeter, it was suggested not to allow the thermometer to touch the bottom of the coffee cup; a few times, because this was so tedious, the thermometer did touch the bottom and that may have affected the results as well. Stirring the solution aids the reaction, but some parts of the experiment may have been stirred more rapidly than others which may have affected the results. Finally, at the beginning of each trial it was recommended to take a reading of the temperature every second, however it was difficult to do this and the temperatures may be off. This lab displayed the functions of the calorimeter accurately due to the fact that the calorimeters are not perfect and do let some heat escape.


Department of Chemistry 2008 First Year Chemistry Chem 120L Laboratory Manual. University

of Waterloo, Waterloo. pp 16-20.

Petrucci, Ralph et.al. General Chemistry Principles & Modern Applications, Ninth Edition.

        Upper Saddle River: Pearson Education, 2007.

This student written piece of work is one of many that can be found in our University Degree Chemistry section.

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Related University Degree Physical Sciences Skills and Knowledge Essays

See our best essays

Related University Degree Chemistry essays

  1. A 0.60 um film of silicon dioxide is to be etched with a buffered ...

    Therefore, the total distance between two opposite sides in the expanded window must be equal to: with significant figures applied where dsides is the total distance between two opposite sides in the expanded window. This length dsides is equal to the dimension of the expanded window after the etching process is complete.

  2. The determination of the molar enthalpy of the combustion of magnesium using Hesss Law

    + 2HCl(aq) � H2(g) + MgCl2(aq) The solid magnesium metal in the form of a ribbon reacts with hydrochloric acid to form a gas and salt. Magnesium Chloride and Hydrogen Gas are produced. This reaction is an exothermic reaction as heat is released.

  1. Determination of the Enthalpy (Heat) of Reaction of a Monobasic Acid with Sodium Hydroxide

    The solution in the calorimeter was allowed to cool. 7. A burette was filled in with 1M of sodium hydroxide solution and clamp onto a retort stand. 8. 25 cm� of the sulphuric acid solution in the calorimeter was pipetted into a beaker.

  2. Optimizing a Windows-Based Computer Data Acquisition and Reduction System for the General Chemistry Laboratory

    During the first week the students were asked to fill out the Kutztown University Chemical Background Information sheet (see Appendix A) which asked questions about their proposed major, career goals, science and mathematics courses completed in high school and college, computer skills, and interest in science and chemistry.

  1. Forensic Chemistry - Ion Selective Electrode. The objective of experiment is to determine ...

    Use the Activity Coefficient to calculate the concentration from the activity. As noted above, the activity coefficient can be calculated for simple solutions with known concentrations of all the ions, but this is not possible in many practical applications, where the samples may have a complex or unknown matrix.

  2. The aims of this experiment are to measure the heat of decomposition of hydrogen ...

    The reaction is carried out inside the vessel, and heat evolved or absorbed is calculated from the temperature change. The experiment involves the decomposition of aqueous H2O2 using Fe(NO3)3 as a catalyst. The decomposition reaction is shown below: 2H2O2 (aq)

  1. The objective of this experiment is to determine how a buffer system resists large ...

    If a small amount of HâO⺠(Hydronium produced by the protonation of water) is added to a buffer solution, the pH decreases, but again not by much because the base component of the buffer solution neutralizes the added HâO⺠illustrated in figure 2 .The change in the buffer agent initially causes little change in the buffer solution’s pH.

  2. EXPERIMENTAL DESIGN: Measurement of Density and Determination of Partial Molar Volume, and the Effects ...

    This fine hole releases a spare liquid after closing a top-filled pycnometer and allows for obtaining a given volume of measured and/or working liquid with a high accuracy. Calibration of the pycnometer to determine its weight and volume was first performed.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work