CHEMESTRY 120-02                                                   2009-09-15
DENSITIES OF SOLIDS AND LIQUIDS

Stefan Martensson C0347318

Procedure: Please refer to handout ‘Experiment #2’ and page 6-8, Chemistry 120 Lab Manual, 2009 Edition, Camosun College.

Data and Results: Temperature: 22˚C, Pressure: 760,6 mm Hg.

Raw Data:
Table A – Raw Data of Unknown Metals 1, 4 and 5.

Table 1 – Mass of Unknown Metals.

Mass of metal was calculated by subtracting the bottle mass (A) from the weight of bottle and metal (B). E.g. unknown metal #1: 62.5070-31.4138=31.0932.
The calculations outlined throughout this report were performed on each of the metals in similar fashion as the example states. The examples are from metal #1.

Table 2 – Determination of the Volume of an Unknown Metal

Mass of dH2O + metal was calculated by subtracting C with B.
E.g. 93.3319-62.5070=30.8249.

Mass of dH2O was done by subtracting D with A.
E.g. 64.8366-31.4138=33.4228.

Mass of dH2O displaced by metal was calculated with this formula: (D-A)-(C-B).
E.g. (64.8366-31.4138)-(93.3319-62.5070)=2.5979

Volume of dH2O displaced by the metal was calculated with the formula: Vol^dH2O = mass^dH2O / density^dH2O. E.g. vol=2.5979/0.99671 => vol=2.6065ml. ml = cm³ so therefore the volume of metal in the bottle is the same number as the volume of displaced dH2O.

Table 3 – Determination of the Density of an Unknown Metal

Mass of the metal was calculated by subtracting the weight of the bottle (A) to the measurement we did with bottle and metal (B). E.g. 62.5070-31.4138=31.0932.

Volume of metal was taken from Table 2.
Density of metal was calculated with the formula: density = mass / volume.

E.g. 31.0932/2.6065=11.9292.

Table 4 – Determination of the Volume of the Pycnometer

Mass of dH2O was calculated by taking the mass of the pycnometer and subtracting it to the total mass of the pycnometer full of dH2O. E.g. 25.8198-15.5901=10.2297.
By calculating the mass of dH2O in the pycnometer, we would be able to use the formula Vol^dH2O = mass^dH2O / density^dH2O gave us the volume of the dH2O and thus the volume of the pycnometer.
E.g. 10.2297/0.99671=10.2635.

Table 5 – Determination of the Density of an Unknown Liquid

After weighing the unknown liquid in the pycnometer, we subtracted the weight of the pycnometer, from Table 4, to get the liquids mass. E.g. 27.6074-15.5901=12.0173.
Density of the unknown liquid was calculated by density^liquid = mass^liquid / Vol^pycnometer.
E.g. 12.0173/10.2635=1.1709.

Discussion

Two sources of errors in this experiment are using the same weighing bottle for all three metals, since lack of carefully wipe the bottle completely will bias the reading. Also the bubbles trapped inside, both connected to the bottles inside and also to the metal.

The use of a stir stick to release the bubbles from the inside works fairly effectively.

Trapped air bubbles would effect the reading by making it seem like the metal were less dense than it actually is, due to air being lighter than dH2O and the metal.

Unfortunately, both the accuracy and precision in density reflected in my findings were not perfect. With the metals #1 & #4 being a bit high and #2 a bit low.

Conclusion

The measured densities of the metals are (the known accurate values within brackets); metal #1: 11.9292g/cm³ lead, Pb (11.4 g/cm³), metal #2: 10.0800g/cm³ which is silver Ag (10.5 g/cm³), metal #4: 2.0247g/cm³ which is magnesium, Mg (1.74g/cm³).

The density of the liquid is 1.1709g/cm³.

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