pls help with all these questions Name: Student No.: Lab Section No.: Pre-lab Qu

Question

pls help with all these questions

Name: Student No.: Lab Section No.: Pre-lab Questions I. Explain why it is important to wear gloves when handling the chromatography paper. 2. What is the stationary phase and what is the mobile phase in this experiment? What would happen in this experiment if the solvent level in the developing chamber was more than 1.5cm high, i. if the sample spots were below the solvent level? 4. Define what is meant by the R, value. If two cations have the same R, value, how could you detect their presence in a mixture using paper chromatography?

Explanation / Answer

1) Answer:

If we touch the chromatography paper, If any compounds on the hand or the sweat of the body contaminates the chromatography paper. Hence we have to wear the gloves.

2) Answer:

Stationary phase:

It is the adsorbent of the impure compound (mixture).

Separation of the different compounds on the column is called sationary phase. In some cases it appears as bands.

In colour compounds we can see the bands.

The stationary phase comes through the mobile phase.

Mobile phase:

Mobile phase generally liquid or gas. When it is eluting through the column, The stationary phases comes along with it with different retention times.

3) Answer:

If the spots are below the solvent leval, The spots of the compound dissolves in the solvent and we connot observe the spots movement on the TLC.

4) Answer:

Rf value:

It is the ratio of distance travelled by compound spot and solvent front.

Rf = Distance travelled by compound spot / Distance travelled by solvent.

If the two compouns are having the same RF value, Then we have to choose the Iodine or charing solutions for the identification of the two different compounds.

With the charing solutions the compounds or ions may appears in different colours.

5) Answer:

Zn2+ travelled = 54 mm solvent front = 94 mm

RF1 = 54 / 94

Another chromatogram

Zn2+ travelled = y (assume) solvent front = 85 mm

RF2 = y / 85

RF1 = RF2

54 / 94 =  y / 85

y = (54 x 85) / 94

y = 5130 / 94

y = 54.574 mm

Hence the band appears at 54.574 mm.

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