Krótkie pytania / Quick questions

[linguoboy]

Can someone explain to me why it's ""pączek z powidłami" and not *"pączek z powidłu"? Especially when it's "pączek z dżemem" and "pączek z marmoladą" not *"pączek z dżemami" or *"pączek z marmoladami".

[pittmirg]

Well, powidła is today generally a plurale tantum. I only use the singular in the expression szwarc, mydło i powidło "miscellaneous things, what not". Why would it be -u, though? I think you got z + Gen. "from" and z + Instr. "with" mixed up.