Taking into account the statement above: "Why do nick and jordan have such a tense conversation? Why is Nick "annoyed" that Jordan has left the Buchanan's house?"
The answer is: The things were getting messy and Jordan started to essentially bailing on the situation. Then, Nick realizes that Jordan cares little for Daisy, Gatsby, or even for him.
Your gonna have to give us a summary of the selection because we don learn the same things you do. After you explain the summary maybe then we can help you with this question.