1.1. A forensic scientist is investigating the ink that has been used to forge the signature on a cheque.

She separates the colours in some inks using paper chromatography.

Look at the diagram of her apparatus.

What is the mobile phase in this experiment?

1.2. Explain how paper chromatography separates the colours in ink.

1.3. Look at the results of the scientist’s experiment.

i) Look at the green spot for ink A. Calculate the R_f value for the green spot.

Answer = ...................................... [2]

ii) Which ink was used to forge the signature on the cheque? Explain how you can tell.

[2]