Assume that if iodine is allowed to migrate freely between equal volumes of water and kerosene, 90% of it will end up in the kerosene and 10% in the water. If you started with 1.0g of iodine total in the water layer, and extracted with an equal volume of kerosene, how much iodine would remain in the water?

If you then discard the kerosene layer and extracted with another equal volue of fresh kerosene, how much iodine would be left in the water?

What total percent of the iodine was removed from the water?

For the first part I thought 0.1 g of iodine will remain in the water since 10% of iodine is in the water. But I don't know if that is right or even how to solve the other parts

You guessed right! You will have 0.1 g of iodine in water and 0.9 g of it in kerosene.

And you work the same way with the next extraction. Could you try it out?