# Molar Volume Lab

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Partial Molar Volume Of A Salt In Aqueous Solution Introduction: The objective of this experiment was to calculate the partial molar volume of a salt in a aqueous solution. This was done my determining the density of binary solutions of sodium chloride and water at different known concentrations. The densities, which were determined using pycnometers, were used to calculate the end goal of the partial molar volumes of the sodium chloride and compare them against the volumes calculated for each solution. Density is defined as “a measure of the compactness of a substance, expressed as its mass per unit volume”. A more simpler way of saying this is that it is the weight of a substance in a given volume. This means that the density of a substance…show more content…
Two clean, dry pycnometers, as seen in Figure 2, were weighed. Then the solutions were placed in the pycnometer one by one and weighed, starting from the least concentration solution, 2% weight by sodium chloride, and going to the highest concentrated solution, 16% weight by sodium chloride. Pycnometer was filled until the solution was at the top of the capillary in the stopper, and then pycnometer filled with solution was weighed. Data: Table 1: Solution Preparation Data Solution % Mass of Salt used (g) Mass of H2O used (g) Moles of Salt used Moles of H2O used Total number of moles, n Mole fraction of H2O, x1 Mole fraction of Salt, x2 2% 1.5495 73.4661 0.0265 4.0780 4.1045 0.9935 0.0065 4% 3.0032 71.9933 0.0514 3.9962 4.0476 0.9873 0.0127 8% 6.0056 69.0051 0.1028 3.8304 3.9331 0.9739 0.0261 12% 9.0320 65.9807 0.1546 3.6625 3.8170 0.9595 0.0405 16% 12.0241 62.9677 0.2058 3.4952 3.7010 0.9444 0.0556 Table 2: Determination of the Density of Solutions Solution % Pycnometer Pycnometer volume (mL) Mass of dry pycnometer (g) Mass of pycnometer & solution (g) Mass of solution (g) Density of solution (g/mL) Avg. density (g/mL) 2% A 25.00 21.0092 46.2520 25.2428 1.0097 0.9956 B 25.00 21.7722 46.3112 24.5390 0.9816 4% A 25.00 21.0092 46.5924 25.5832 1.0233 1.0093 B 25.00 21.7722 46.6519 24.8797…show more content…
The solution were tested in such a way that the densities determined with accurate, and were used in the calculations of partial molar volumes. The partial mole volume of sodium chloride in the 2%, 4%, 8%, 12%, and 16% weight by sodium chloride solutions were found to be 1.969*10-5, 1.955*10-5, 1.94*10-5, 1.948*10-5, and 1.979*10-5 m3/mol respectively. From the graph generated of total molar volume vs. the mole fraction of sodium chloride, see MathCAD page 5, there is a positive trend between the total molar volume and the mole fraction of sodium chloride. The slope of 1.349*10-5 m3/mol demonstrates this theory. This is to say that there is molecular interaction between the water molecules with the sodium and chloride