A mixture placed in an Erlenmeyer flask comprises of 6ml of silica gel and 40ml of solvent containing, in solution, 100mg of a non-volatile compound. After stirring, the mixture was left to stand before a 10ml aliquot of the solution was extracted and evaporated to dryness. The residue weighed 12mg.

Calculate the adsorption coefficient K=C(stationary phase)/C (mobile phase) of the compound in this experiment.

Question

A mixture placed in an Erlenmeyer flask comprises of 6ml of silica gel and 40ml of solvent containing, in solution, 100mg of a non-volatile compound. After stirring, the mixture was left to stand before a 10ml aliquot of the solution was extracted and evaporated to dryness. The residue weighed 12mg.

Calculate the adsorption coefficient K=C(stationary phase)/C (mobile phase)   of the compound in this experiment.

aaronq · Answer

do you understand what's going on?

anonymous · Answer

Not really for this question. For the other chromatography question I can solve them using the equations given and relationships between them, but this one I have no clue.

aaronq · Answer

so you had 100 mg of a compound,  40 mL of solvent and 16 mL of gel.

now, you mixed it and sampled a 10 mL portion of the solvent and found 12 mg of the compound.

10 mL is i quarter of the 40 mL total, so 12 mg*4= 48 mg of the solute is in the solvent, (100-48mg)=52 mg is adsorbed to the gel.

can you finish it now?

anonymous · Answer

okay say 52mg is adsorbed into the gel what is the relationship between the math you did and the equation shown above?

aaronq · Answer

adsorption coefficient, K=C(stationary phase)/C (mobile phase)   

C = concentration

stationary phase = gel
mobile phase = solvent

anonymous · Answer

concentration = mol/vol
i cant get mol

aaronq · Answer

concentration can be anything, you obviously can't use moles, use mg/mL