1. F or compounds having similar Rf values, what could be altered to improve the

Question

1. F or compounds having similar Rf values, what could be altered to improve the the spots? 2. Why are small concentrated spots of sample applied to the plate? 3. Calculate the Rf values for the each of the spots shown on the plate below A B 4. If two compounds have Rr values of 0.60 and 0.29, how far will they be separated from each other on a plate when the solvent front is developed to: (a) 3.0 cm? (b) 12 cm? 5. During development a compound continually exchanges locations between the moving solvent and the stationary silica gel. How much it moves depends on how well it sticks to the silica and how well it is solvated. If you have a single compound, how would changing the eluting solvent from toluene to acetone affect the Rr value? Explain your answer. See pg. 183 more info.

Explanation / Answer

1) we can change the solvent and opt a one that allows better separation of the spots.

2) This is done in order to improve accuracy, becuase small and concentrated sample spotting on plate give sharp and a point like spot on TLC plate after developing.

3) Rf value for A = distance moved by solute A / distance moved by sovent front

Rf value for B = distance moved by solute B / distance moved by sovent front

4)

a) using above formula for compund A,

0.6 = distance moved by solute A / 3 cm

1.8 cm = distance moved by solute A

Similarly, for B

0.29 = distance moved by solute B / 3 cm

0.87 cm = distance moved by solute B

So, difference in the distance = 1.8 - 0.87 = 0.93 cm

b) proceeding in a similar way when solvent front = 12 cm

distance moved by solute A = 7.2 cm

  distance moved by solute B = 3.48 cm

Difference in the distance = 7.2 - 3.48 = 3.72 cm

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

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