Tin and Nitric Acid

Jarrett Sears Dr. Hummel Chem 121 2/7/13 A Chemical Reaction between Tin and Nitric Acid Introduction: Finding the products made from the components of tin metal and nitric acid is the ultimate objective of this lab; the formula of the products will be found in the CRC handbook thereafter. Procedure: First, obtain a clean crucible, and heat it under a Bunsen burner until it is as hot as possible, about 15 minutes within a fume hood unit. The Bunsen burner will be used under the fume hood for the entire duration of the lab. Place a crucible on a wire gauge, and wait for the crucible and its lid to cool off completely.After cooling, obtain the weight of the crucible and lid by placing it on a petri dish to be placed on an electric balance (petri dish mass must be obtained prior) without using any hands; there will not be any touching of the fingers or hands to or on the crucible and subtract the mass of the petri dish to obtain the mass of crucible. (Mass is noted at 61. 805g with cruc ible and petri dish, crucibles mass: 25. 253g) tin is weighed between 0. 9000g and 1. 0g (for this expirement, . 98g is weighed) and added to the crucible, which is placed back onto the non. ignited Bunsen burner.While the crucible is being held by the Bunsen burner stand, 10M Nitric acid is dropped into the crucible with the tin unitil there is no longer any kind of reaction from it. This takes nearly 100 drops. It will bubble and fumes will arise. When nothing further occurs after ten minutes, the Bunsen burner is lit with the tin and nitric acid inside. Heat for about 15 minutes, let the crucible with the now contained tin oxide, cool on the wire gauze again and measure its mass. Repeat the heating process without adding anything to the crucible for an additional 15 minutes.After finding the mass of the tin oxide, by subtracting the initial weight of the crucible from the weight of the crucible with the tin oxide, we can compare the two measurements. Data: Grams Petri dish36. 552 With Crucible61. 805 Crucible alone with lid25. 253 Tin0. 98 After first run63. 043 Tin oxide:1. 238 Drops of nitric acid:100 Measured Oxygen:0. 258 2nd run of oxygen0. 253 Mass percentage of Tin: Oxygen79. 2%:20. 8% Moles of tin0. 0083 Moles of oxygen0. 01612 Discussion: After the nitric acid is applied to the tin filled crucible, the reaction has already began, after only a few drops, fumes start venting out of the crucible.There is . 98g of tin in the crucible; the nitric acid applied (100 drops: it is not necessary to weigh this for the ultimate objective of finding tin to oxygen ratio) may weigh 3 grams (hypothetically). There would be a net mass of 3. 98 grams, but due to the fumes of the reaction, some of this net mass is lost already before the burner is even turned on. This proves true even further once the burner is lit; brown fumes will be emitted from the crucible that we find later to be nitrogen dioxide in the CRC handbook. After heating and cooling, the crucible is n ow 1. 238g heavier than the empy crucible.After equating the mass of the now tin oxide, 1. 238g, we now find the tin to oxygen ratio. There is . 98 g of tin and . 258g of oxygen in this product, dividing this by their respective quantity of AMU found via the periodic table will give us the number of moles, 0. 0083 moles of tin in 0. 98 grams, or 8. 3 X10(3rd). There are 0. 01612 moles of oxygen in 0. 258 g of oxygen or 1. 612X10(3rd) this is the mass combined to the tin. When we divide these moles by the smaller figure, we then learn the empirical formula; this is our 1:2 ratios are found. Oxygen consists of 20. percent of the final mass, while tin is the remaining 79. 2%. Nitrogen is found by process of elimination, four different oxides of nitrogen are looked up in the CRC handbook: HNO3, NO, N2O, and NO2. NO2 is the only gas that is brown amongst this group. Sources of error would entail heating the crucible for duration of time too short for the reaction to finish, resulting in a heavier compound, and jeopardizing the legitimacy of the entire experiment. It could potentially leave the demonstration with nothing to be learned if there is not a 1:2 ratio after finding the inaccurate molar masses.Conclusion: This is to understand how reactions occur, and sometimes need more than to just be mixed together, heat is needed. Also, the ratio of mass does not infer ratio of atoms, far from it. The 1:2 tin oxide ratio results when one molecule of tin (Sn) combines with 2 nitric acid molecules (2HNO3), and the hydrogen is released as NO2 (byproduct) this is the fume referred to prior, where the value of mass is lost and the remains are the product of tin oxide: SnNO2. The mass of the tin far outweighs that of oxygen by nearly 60%, yet consists of only two thirds of the molecular ratio. Sn +2HNO3 > SnO2+2NO2+H2