The objective of this procedure is to determine the identity of three unknown samples by using two different tests: The Iodoform test and the Tollen’s test.
Procedure Part A- Iodoform Test
• In three clean and empty test tubes, three drops of each respective unknown liquid were inserted via pipette to their respective labeled test tube (which were labeled according to whatever compound they would contain, i.e. A, B or C). These test tubes were subsequently treated with 2 mL of water and 2 mL of 10% aqueous sodium hydroxide (NaOH) solution each. Additionally, 3 mL of a 10% solution of Iodine were added dropwise into each test tube; great care was taken to ensure that only the necessary amount of solution was added, meaning until an expected …show more content…
Afterwards, one drop of 10% aqueous sodium hydroxide (NaOH) was added to every test tube, and they were all thoroughly shaken. It was observed that the solutions developed an excessive amount of a brown solid. Additional drops of 2% aqueous ammonia were added until the precipitate had dissolved completely. It was emphasized that excess ammonia should be avoided, since it could affect the results of the test by affecting the production of the Tollens’ reagent, and it was also emphasized that these solutions should be added in this exact order. After adding the drops of 2% aqueous ammonia, the Tollens’ reagent was completed, and 2 drops of every respective compound were added and the test tube was shaken. The test tubes were allowed to sit for 10 mins, and in those 10 mins it was determined if a positive or negative result was observed. In the case of a positive result, the solution would begin forming small silver “mirrors”, or also a black precipitate. The observations and results for this test, as well as those for the Iodoform test, are illustrated in Table 1 and Table 2. Additionally, the mechanism that illustrates the way this test functions can be found in Mechanism 1.B. The compounds and solutions from this test were disposed of differently; since the Tollens’ reagent can produce dangerous silver nitride …show more content…
Considering the observations in Table 1, it can be determined that compound A was the only positive result, since there was a formation of the expected silver “mirrors”. Additionally, compounds B and C can be considered negative results since there was no precipitate developed. Considering this, and considering the mechanism for this test’s reaction (see Mechanism 1.B), it can be concluded that compound A must be some kind of aldehyde (since Mechanism 1.B point out that the reaction relies on the aldehydes ability as a reducing agent in order to reduce silver ammonium nitrate into elemental silver). Therefore, it can be speculated that compound A is benzaldehyde, and that at the very least compounds B and C cannot be aldehydes. This kind of test works very well with the given possible identities since the test’s reaction will only occur with an aldehyde reagent (which there is only one in the given list). And unlike the iodoform test, this procedure was strictly followed given the fragility of the Tollen’s reagent and the danger of the reagents and the products. As such, the procedure performed exactly as expected and perhaps the only room for improvement would be to perform the test in a more diligent manner in order to complete the procedure in the
Procedure Part A- Iodoform Test
• In three clean and empty test tubes, three drops of each respective unknown liquid were inserted via pipette to their respective labeled test tube (which were labeled according to whatever compound they would contain, i.e. A, B or C). These test tubes were subsequently treated with 2 mL of water and 2 mL of 10% aqueous sodium hydroxide (NaOH) solution each. Additionally, 3 mL of a 10% solution of Iodine were added dropwise into each test tube; great care was taken to ensure that only the necessary amount of solution was added, meaning until an expected …show more content…
Afterwards, one drop of 10% aqueous sodium hydroxide (NaOH) was added to every test tube, and they were all thoroughly shaken. It was observed that the solutions developed an excessive amount of a brown solid. Additional drops of 2% aqueous ammonia were added until the precipitate had dissolved completely. It was emphasized that excess ammonia should be avoided, since it could affect the results of the test by affecting the production of the Tollens’ reagent, and it was also emphasized that these solutions should be added in this exact order. After adding the drops of 2% aqueous ammonia, the Tollens’ reagent was completed, and 2 drops of every respective compound were added and the test tube was shaken. The test tubes were allowed to sit for 10 mins, and in those 10 mins it was determined if a positive or negative result was observed. In the case of a positive result, the solution would begin forming small silver “mirrors”, or also a black precipitate. The observations and results for this test, as well as those for the Iodoform test, are illustrated in Table 1 and Table 2. Additionally, the mechanism that illustrates the way this test functions can be found in Mechanism 1.B. The compounds and solutions from this test were disposed of differently; since the Tollens’ reagent can produce dangerous silver nitride …show more content…
Considering the observations in Table 1, it can be determined that compound A was the only positive result, since there was a formation of the expected silver “mirrors”. Additionally, compounds B and C can be considered negative results since there was no precipitate developed. Considering this, and considering the mechanism for this test’s reaction (see Mechanism 1.B), it can be concluded that compound A must be some kind of aldehyde (since Mechanism 1.B point out that the reaction relies on the aldehydes ability as a reducing agent in order to reduce silver ammonium nitrate into elemental silver). Therefore, it can be speculated that compound A is benzaldehyde, and that at the very least compounds B and C cannot be aldehydes. This kind of test works very well with the given possible identities since the test’s reaction will only occur with an aldehyde reagent (which there is only one in the given list). And unlike the iodoform test, this procedure was strictly followed given the fragility of the Tollen’s reagent and the danger of the reagents and the products. As such, the procedure performed exactly as expected and perhaps the only room for improvement would be to perform the test in a more diligent manner in order to complete the procedure in the