E5.docx

Introduction The partial molar quantity of a substance expresses the change in per mole of the component of any extensive property such as enthalpy, entropy, Gibbs energy, volume, etc. of a component of a singlephase system. For this to hold true, the system must remain at a constant pressure and temperature.[1] Meanwhile, the partial molar volume of a substance presents the contribution of one component in a mixture to the overall volume of a sample. The concept of partial molar volumes has a practical application in the field of metallurgy such as in alloying.[2] The partial molar quantities of a system can be determined using the following equations: ∗ 𝑉 = 𝑛𝐻2𝑂 𝑉𝐻20 + 𝑛𝑁𝑎𝐶𝑙 𝜑𝑁𝑎𝐶𝑙 [1]

𝑉 = 𝑛𝐻2𝑂 𝑃𝑉𝐻2𝑂 + 𝑛𝑁𝑎𝐶𝑙 𝑃𝑉𝑁𝑎𝐶𝑙 [2] where V is the volume of the solution 𝑛𝑖 is the number of moles of i in solution ∗ 𝑉𝐻20 is the molar volume of pure H2O

The partial molar volume is highly affected by the solvation effect. Solvation is a process that highly depends on the kinetics of the solution and is expressed by its rate. Solvation occurs when the ions in the solution interact with the solvent. This occurs due to the high interaction present between the solvent and the dissolved ions which makes them bounded together by ion-dipole forces or covalent bonds. This leads to the decrease in volume of the solution by enclosing the other solute with the solvent forming solvation shells thereby lessening its total volume contribution.[3] In measuring the partial molar volume of substances, an apparatus such as a pycnometer is used. A pycnometer is a glass bottle with a vented stopper which can hold liquids of 2 cm3 – 100 cm3 and is usually used for density measurements.[4] In this experiment, the partial molar volumes of sodium chloride were determined thru density measurements using a pycnometer. The theories and techniques concerning partial molar volume were applied and practiced in this experiment. Methodology The materials used in this experiment were varying concentrations of sodium chloride solutions, distilled water, pycnometers, thermometer, volumetric flasks, pipettes, acetone, and lint free wipes. For the preparation of solutions, varying concentrations of sodium chloride were prepared thru successive volumetric dilutions resulting to 250 mL solutions of 1.5 M, 0.75 M, 0.375 M, 0.1875 M, and 0.09375 M of sodium chloride. The pycnometer was first rinsed with distilled water and with acetone prior to calibration. It was oven dried, and weighed until a constant weight was obtained. The pycnometer was filled with water and placed in a water bath until it reached equilibrium. Afterwards, the pycnometer was removed from the water bath, wiped dry with lint free wipes, and was weighed. The same procedure was performed for the different concentrations of sodium chloride. References:

[1] Cammack, R., ed. Oxford Dictionary of Biochemistry and Molecular Biology. NY: Oxford University Press, 2006. Accessed November 25, 2017. http://app.knovel.com/hotlink/toc/id:kpODBMBE01/oxforddictionary-biochemistry/oxford-dictionary-biochemistry. [2] Shamsuddin, M. Physical Chemistry of Metallurgical Processes. NJ: John Wiley & Sons, Inc., 1945. [3] Buncel, Erwin, and Robert A. Stairs. Solvent Effects in Chemistry. 2nd. ed. NJ: John Wiley & Sons, Inc., 2016. [4] Wilhelm, Emmerich, and Trevor M. Letcher, eds. Volume Properties Liquids, Solutions and Vapours. UK: The Royal Society of Chemistry, 2015.