"Už jsi umyl to nádobí?"

Translation: Did you do those dishes yet?

[judygunson]

Why is "Have you already done the dishes" wrong?

[VladaFu]

We require "those dishes", see my other comment.

[Travis0]

Or, have you washed those dishes yet

[VladaFu]

Here we require "those dishes" for "to nádobí". As "to wash the dishes" is just "mýt nádobí".

Wash/Do the dishes! Umyj nádobí!

[Paul378887]

Why is it not “...ty nádobí”?

[AgnusOinas]

It's a collective noun and it's singular neuter.