Laboratory work no.1 english (0)

Aim of the work
Creating a solution from solid compounds, separating compounds from mixtures using their differences in solubility, determining the percentage of table salt in a sand -salt mixture.
Used compounds
Solid sodium chloride in a mixture with sand, dried to a constant weight at 105ºC.
Equipment
Beaker, glass rod, funnel, conical flask, measuring cylinder (250 cm3), hydrometer, filter paper .
1) In a conical flask, dissolve the NaCl from a previously weighed sand-salt mixture. To do that, add about 50 cm3 of distilled water to the mixture. Stir the solution with a glass rod and then filter it. Figure 1.1
Figure 2.1
For filtration, fold the filter paper in half twice. Cut one corner for the filter paper to distribute evenly to the wall of the funnel (see figure 1.1).
Place the filter paper into the funnel, wet it with distilled water and press it firmly against the wall of the funnel. While filtering , try to leave as much insoluble material in the conical flask as possible. Pour the solution on the filter, letting the solution flow along the glass rod (figure 1.2). The glass rod must be slightly tilted and cannot touch the bottom of the filter as it may break easily. See that the glass rod is in the solution at all times and not on the desk . Figure 1.2
Place the beaker under the funnel so that the longer edge of the stem is placed against the wall of the beaker. This ensures the constant flow of the filtrate along the wall of the beaker so there is no chance of drops escaping from the beaker.
Fill the filter to 3/4 and immediately place the glass rod back into the conical flask.
2) For washing the NaCl out of the sand, add another 50 cm3 of distilled water to the residue in the conical flask and filter it again into the beaker through the same filter paper. Repeat this once more. In the end wash the filter to carry all of the dissolved salt into the solution. To do that, fill the filter with distilled water and let it drain until the end.
Rinse the sand into the sand collector with tap water.
3) Pour the clear filtrate from the funnel into a measuring cylinder and then fill it to 250 cm3 with distilled water. Carefully and thoroughly mix the solution by turning the measuring cylinder over many times.
4) Use the hydrometer to determine the density of the solution. See that the hydrometer doesn’t touch the wall of the measuring cylinder while measuring. After measuring, wash the hydrometer with tap water, rinse it with distilled water and dry it.

Results of experiment

Measuring with areometer we got density of sand-salt mixture no.7:
Volume of solution:

Calculations

1) Using given tabel of „ Dependence of solution density to the percentage of NaCl in a solution “, taking the closest number to result :
To these densities equals percentages:
To get right percentage of the solution:
2) Calculation of the mass of natrium chloride mNaCl in the solution using the results of measurement (solution volume and density):
3) Finding the molar concentration of the NaCl solution. The molar mass of NaCl is 58.5 g/mol.:
Molar mass of NaCl:
Calculation:
4) Calculation of percentage of NaCl in sand-salt mixture:
Given mass of the mixture:
5) Actual percentage of NaCl (given):
Calculation of actual mass:
Calculation of the systematic error of the test:

Conclution

Through this experiment I got percentage of NaCl in sand-salt mixture 77,56%. As it was given that percentage of NaCl is 80%, we can consider our result as quite accurate as error was less than 10% (3,14%