Required Practical 7

Question 1

How to calculate Rf value

Answer 1

Rf = distance moved by pigment from origin to centre of pigment spot
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Distance from origin to solvent front

Question 2

You were told to draw a line to show the solvent front before the filter paper dried. Explain why it was necessary to draw the line before the filter paper dried

Answer 2

Because the paper would dry and the solvent front would no longer be visible

Question 3

Explain why it would be better to use the Rf value to do this and not the distances moved by the pigment spots.

Answer 3

The solvent front value might be different.
Rf values are more consistent

Question 4

You were told not to move the bottle once you had put the TLC paper in it. Suggest why this is important

Answer 4

So the pigment would not run straight off the paper

Question 5

Explain why you should measure to the centre of the pigment spot

Answer 5

Standardised readings so comparisons can be made

Question 6

Give one dependent variable used to measure the rate of photosynthesis in aquatic plant

Answer 6

Count number of bubbles