The data for solvent system 1 was 5.4 cm for distance traveled and for solvent s

Question

The data for solvent system 1 was 5.4 cm for distance traveled and for solvent system #2 it was 5 cm.the TLC data for solvent 1 is 2cm with an Rf of .37 making it ibuprofen, caffeine was 0, aspirin 1.6cm with .29Rf, acetaminophen and the mystery sample were 0.
For solvent 2 : Rf .78 was ibuprofen, caffeine.12, aspirin .60, acetaminophen.38, and .54 for the mystery sample 5 Did you use the Tuc plate run in solvent system 1 or 2 to determine the identity of your analgesic sample? Explain 2 Explain how your Tuc data allowed you to determine the identity of your mystery analgesic sample 3 Determine each of the following from the TLc data you used to identify your analgesic sample. a The analgesic ingredient that has a polarity most similar to the stationary phase b The analgesic ingredient that has a polarity most similar to the mobile phase 4 Why is it not possible to have an R, value greater than 1.00? A student used a pen rather pencil to the origin on a TLC plate. Explain how this could be a proble for than a mark the TLC experiment.

Explanation / Answer

1.

From the data obtained, we can see that mystery sample show Rf value 0 in solvent system 1 whereas it is 0.54 in solvent system 2. It is impossible to identify the substance if it has Rf value 0 , because Rf value 0 shows that the sample has not moved at all. Therefore it is ideal to choose solvent system 2 for TLC plate run.

2. We can do separate TLC plate run for the known analgesics & can obtain Rf values for each one. Then the mystery sample can be run using the same solvent system and Rf value can be noted. We can then compare the Rf value of mystery sample with the known Rf values and whichever known value coincides with the mystery sample must be the mystery sample ingredient .

From the data we can say that mystery ingredient has Rf value nearer to that of Aspirin. So it is likely that the mystery ingredient is Aspirin

3. We will consider data for solvent system 2

a. The substance that has lowest Rf value is Caffeine with Rf = 0.12. Low Rf value shows that the substance has more affinity towards stationary phase and is therefore eluted first. This suggests that the analgesic ingredient that has polarity similar to that of stationary phase is Caffeine

b. The substance that has highest Rf value is Ibuprofen with Rf = 0.78. This shows that the substance has affinity towards mobile phase and therefore is retained in the mobile phase for a longer time. This suggests that the analgesic ingredient that has polarity most similar to mobile phase is Ibuprofen

4 The formula to calculate Rf value is

Rf = Distance travelled by the solute / Distance travelled by the solvent

Since the solute is dissolved in the solvent, distance travelled by the solvent would always be more . As a result denominator in the formula would always be higher and therefore it is not possible to get Rf value greater than 1

5.The pencil is made of a substance known as graphite. This is extremely non polar substance and therefore it would never dissolve in polar mobile phase. On the other hand pen ink is a mixture of different kinds of dyes and other possible polar ingredients. Therefore there are chances that these ingredients might dissolve in mobile phase and interfere with the solute. We can see ink ingredients getting dragged along with mobile phase and this would make finding Rf of desired ingredients difficult.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.