Umm no I have no idea what happens in the reaction or how to write a reaction equation, I think its just the wording of the question I think its supposed to say potassium sodium tartrate, not sodium tartate. Because theres a note on my question sheet that says: Note we want 3% (wv) sodium tartrate, not 3% sodium tartrate tetrahydrate. So I think they just forgot to mention potassium.