CHM170L Exp5 Heat of Solution

CHM170L Physical Chemistry 1 Laboratory 4th Quarter SY 2009-2010

Heat of Solution Nieva, Aileen D.1, Arceo, Mary Anne V., Cuales, Jelline C., Kim, Sung Min, Ngan, Emil Joseph T., Rivera, Jainie Lynne B.2 Professor, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology; 2Student (s), CHM170L/A41, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology 1

ABSTRACT The abstract is a condensed version of the entire lab report (approximately 250 words). A reader uses the abstract to quickly understand the purpose, methods, results and significance of your research without reading the entire paper. Abstracts or papers published in scholarly journals are useful to you when you are conducting library research, because you can quickly determine whether the research report will be relevant to your topic. The material in the abstract is written in the same order as that within the paper, and has the same emphasis. An effective abstract should include a sentence or two summarizing the highlights from each of the sections: introduction (including purpose), methods, results, and discussion. To reflect the content (especially results and conclusions) of the paper accurately, the abstract should be written after the final draft of your paper is complete, although it is placed at the beginning of the paper. Begin the abstract with a brief, but specific, background statement to introduce your report. State your main purpose or objective and hypothesis. Describe the important points of your methodology (species/reagents/ingredients, the number of subjects or samples, and techniques or instruments used to make measurements). Summarize the main results numerically and qualitatively (include standard errors and p values as required). Summarize the major points from the discussion/conclusion. Focus on the points that directly relate to your hypothesis/question. For each type of information, use the same tense as in each corresponding section (i.e., past tense for methods and results, present tense for theory and conclusions).

Keywords: albumin, casein, invertase, Bradford Assay, Warburg-Christian Assay, Benedict’s reagent

INTRODUCTION The enthalpy change of solution (or heat of solution) is the enthalpy change associated with the dissolution of a substance in a solvent at constant pressure. The enthalpy change of solution is one of the three dimensions of solubility analysis. It is most often expressed in kJ/mol at constant temperature. Just as the energy of forming a chemical bond is the difference between electron affinity and ionization energy, the heat of solution of a substance is defined as the sum of the energy absorbed, or endothermic energy (expressed in "positive" kJ/mol), and energy released, or exothermic energy (expressed in "negative" kJ/mol). Because heating decreases the solubility of a gas, dissolution of gases is exothermic. Consequently, as a gas continues to dissolve in a liquid solvent, temperature

Experiment 05│ Group No. 4│ 18 May 2010

will decrease, while the solution continues to release energy. This is an effect of the increase in heat or of the energy required to attract solute and solvent molecules in other words, this energy outweighs the energy required to separate solvent molecules. When the gas is "completely" dissolved (this is purely theoretical as no substance can infinitely dissolve)—the heat of solution will be at its maximum. Dissolution can be viewed as occurring in three steps: 1. Breaking solute-solute attractions (endothermic), see for instance lattice energy in salts. 2. Breaking solvent-solvent attractions (endothermic), for instance that of hydrogen bonding 3. Forming solvent-solute attractions (exothermic), in solvation.

1 of 3


METHODOLOGY Experimental Procedure: Heat of Solution Measurement using Parr 1455 Solution Calorimeter A. Heat of Solution of Different States 1. Measurement at least 0.5000 g of sodium chloride and place it in the Teflon dish. 2. Measure 100 ml of distilled water and place it in the Dewar flask. 3. Set-up the Parr 1455 Solution Calorimeter. Press F1 to begin the initialization stage. Note down the sample ID and press ENTER. 4. Input The Exact weight of the sample and press ENTER 5. Wait for the first “beep” and fire the push rod and press ENTER. 6. Wait for the second “beep” and press DONE 7. Browse the result using the arrow up (↑) and down (↓) keys. 8. Clean the Solution Calorimeter for the next sample. 9. Repeat procedures for the next samples.

Before conducting the experiment, the laboratory instruments used in the experiment must be familiarized. The equipments used are the following:

Parr 1455 Solution Calorimeter

analytical balance

100-ml graduated cylinder

Reagents: sodium chloride, ammonium chloride, calcium chloride, water

sodium chloride

ammonium chloride

Treatment of Results: Compare the heat of solution of the three samples. Differentiate between the endothermic and the exothermic reaction based on the results. Discuss the effect of changing the concentration of a solution with respect to its heat of solution.


calcium chloride

water

Before proceeding to the experiment, all of the apparatus were prepared, cleaned using chromic acid, rinsed with distilled water and calibrated by the lab assistant.

2 of 3


For the experiment proper of part A (Heat of Solution Measurement using Parr 1455 Solution Calorimeter), at least 0.5000 g of sodium chloride (sample) and a 100 ml of distilled water were measured using a digital balance and a graduated cylinder respectively. The samples were placed on a clean Teflon dish, which was wiped using a tissue, and in the Dewar flask respectively. The Parr1455 Solution Calorimeter setup was prepared and F1 was pressed to begin the initialization stage. The sample ID was noted and ENTER was pressed. The mass of the sample was acquired using a digital balance. The sample must be completely dry to avoid error. The exact weight of the sample was inputted in the machine and ENTER was pressed. When the first “beep” was heard, the push rod was fired and ENTER was pressed. It took at least 15 minutes for the second long beep to be heard. After hearing the first beep, DONE was pressed. The experiment took long because of the errors such as machine failure encountered during the experiment proper. The results were browsed using the arrow up (↑) and down (↓) keys. The Solution Calorimeter was cleaned for the next sample and the procedures were repeated for the other samples. RESULTS AND DISCUSSIONS

REFERENCES http://en.wikipedia.org/wiki/Heat_of_solution http://en.wikipedia.org/wiki/Exothermic_reaction http://en.wikipedia.org/wiki/Endothermic


3 of 3

CHM170L Exp5 Heat of Solution

Recommend Documents