rp 7 Flashcards
chromatography
1
Q
why must the origin line be drawn in pencil not pen?
A
ink from the pen will dissolve in the solvent and run
2
Q
why should you draw a line where the solvent reached immediately?
A
the solvent evaporates rapidly so the end position isn’t visible shortly after the experiment
3
Q
why should you measure the rf value from the middle of the pigment value?
A
the pigment mark is spread out so by measuring from the middle position each time it’s a way to standardise the measurements you’re taking to allow for comparisons
4
Q
why should you make sure your chromatography paper is vertical and straight?
A
so the pigments move straight up the paper to avoid them running off the side the paper and being washed off
