"Take my money and buy something with it."
Translation:Neem mijn geld en koop er iets mee.
Why does the ermee needs to be "separated" in this sentence and say "er iets mee" instead?
I don't know the grammar rules, but both koop er iets mee and koop iets ermee are correct, the former is more common. It sounds more natural if you ask me. I think this works similar for e.g. hiermee, daarmee, ervan, hiervan, daarvan, erop, etc.. These are also commonly split when combined with niet.