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Kevin LeeChem 219 MW 10:15am-3:00pmLab Report 22/17/11

THE FORMULA OF A COMPOUND FROM EXPERIMENTAL DATA

I. Objective: The purpose of this laboratory experiment is to determine the molecular formulas of two

types of compounds, silver chloride and tin oxide.

II. Equation:A) Part 1: Chloride of Silver

Ag + 2 HNO3 AgNO3 + 2NO + H2O

2HNO3 H20 + 2NO + O2

AgNO3 + HCl AgCl + HNO3

B) Part 2: Oxide of Tin: *** NO EQUATIONS***

III. Materials: Evaporating dish Evaporating dish tongs Watch glass Balance

Meker burner Flame Starter Ring stand

IV. Procedure:

A)Part 1: Chloride of SilerFirst, a clean evaporating dish was heated for 20 minutes. It was, then, let cool to room

temperature and transferred to balance for weighing by using a tongs. The weight of the empty dish after the initial heating and cool was carefully recorded. About 0.5-1g of dry pure silver metal was added to the dish. The dish with silver metal was weighed again and recorded.

Next, silver was dissolved in the dish by adding of 10mL dilute 6M HNO3. The dish was covered with watch glass and warmed up with low flame. Attention was taken to make sure there wasn’t any loss of solution. When the silver was completely dissolved, the bottom of the watch glass was rinsed with distilled water into the dish.

Then, approximately 4mL of 6M HCL was added to the solution and the entire content was mixed gently by rotating the dish around. Precipitation completeness was tested with additional 3 drops of HCl. The content was then heated up to evaporate via boiling water bath.

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When the precipitate was apparently dry, the dish was heated cautiously under the direct flame with wire gauze. Heating continued until all vapors of water and acid were gone. The dish was let cool and weighed again and again until it was constant to the mass. Weight of dish was recorded the data below.

V. Data: A)Part 1: Chloride of Siler

1. Mass of evaporating dish 74.8475g

2. Mass of evaporating dish and silver 75.7247g

3. Mass of evaporating dish and silver chloride 76.0040g

VI. Calculations: A)Part 1: Chloride of Siler

1) Mass of silver: 75.7247g - 74.8475g = 0.8772g2) Mass of silver chloride : 76.0040g - 74.8475g = 1.1565g3) Mass of chloride: 1.1565g - 0.8772g = 0.2793g

0.8772g Ag x (1mol Ag / 107.9g Ag) = 0.008130 mol Ag / 0.007879 = 1 Ag0.2793g Cl x (1mol Cl/ 35.45g Cl) = 0.007879 mol Cl/ 0.007879 = 1 Cl

Molecular formula of silver chloride: AgCl

Experimental % Ag metal: (0.8772g / 1.1565g) x 100% = 75.85%

Theoretical % Ag metal: (107.9g Ag/ 143.35g AgCl) x 100% = 75.27%

% Error = (%Exper - %Theor) / % Theor x 100% = (75.85% -75.27%) / 75.27% x 100% = 0.7%

VII. Observation and Disscussion:

In the dissolving step, silver must be completely dissolved in nitric acid before the subsequent reaction with hydrochloric acid to occur with expected rate. In the final step of heating, the vapor of water must be completely evaporated from the dish or experimental data will not be accurate. There was no change in color of solid residue of silver chloride at the end of the heating process. The Experimental % of Ag metal was 75.85%, and Theoretical % of

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Ag metal was 75.27%. The percent error for the experiment was 0.7%. The 0.7% error is within the acceptable range for the experiment. This experiment was conducted quite accurate.

IV’. Procedure:

B)Part 2: Oxide of TinFirst, a clean evaporating dish was heated. It was, then, let cool to room temperature and

transferred to balance for weighing by using a tongs. The weight of the empty dish after the initial heating and cool was carefully recorded to precision of 0.001g. About 0.5g of tin foil was added to the dish. The dish with tin was weighed again and recorded. The dish was, then, covered with a watch glass and 10mL of 6M HNO3 was added via the lip of the dish.

Then, the dish was warmed up slightly on a water boiling bath to dissolve the metal without loss of solution.

Next, the reaction was extended for 20 to 45minutes. Then, watch glass was rinsed. The solution was evaporated via a water bath. When the content inside the dish appeared dry, the dish was transferred to wire gauze for final heating with caution not lose any materials inside the dish

Heat was kept gently until material became dry. Once the content was dried out completely, intense heat was applied. Color of the content was observed and recorded. Cooling and weighing were repeated until the weight of the dish was at constant mass.

V. Data: B)Part 3: Oxide of Tin

4. Mass of evaporating dish 74.8346g

5. Mass of evaporating dish and tin 75.3295g

6. Mass of evaporating dish and tin oxide 75.4501g

VI. Calculations: B)Part 1: Oxide of Tin

1) Mass of tin: 75.3295g - 74.8346g = 0.4949g2) Mass of tin oxide: 75.4501g - 74.8346g = 0.6164g3) Mass of oxygen: 0.6164g - 0.4949g = 0.1215g

0.4949g Sn x (1mol Sn / 118.7g Sn) = 0.004169 mol Sn / 0.004169 = 1 Sn0.1215g O x (1mol O/ 16.00g O) = 0.007590 mol O/ 0.004169 = 1.82 = 2 O

Molecular formula of silver chloride: SnO2

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Experimental % Sn metal: (0.4949g tin / 0.6164g tin oxide) x 100% = 80.28%

Theoretical % Sn metal: (118.7g Ag/ 150.7g SnO2) x 100% = 79.13%

% Error = (%Exper - %Theor) / % Theor x 100% = (80.28% -79.13%) / 79.13% x 100% = 1.45%

VII. Observation and Disscussion:

Heat was kept gently during the reaction of nitric acid in the boiling water bath so that the content of the solution was preserved, not being decompose. Before intense heat, the solution must be apparently dry. This will also helps keep the integrity of sample.

In the intense final heating step, the residue appeared yellow at first, but then turned to whitish at last. The Experimental % of Sn metal was 80.28%, and Theoretical % of Sn metal was 79.13%. The percent error for the experiment was 1.45%. Since the % error lies within the acceptable range of 3%, the data collected and the steps performed in this part of experiment were acceptable.