It depends on the keyword and how much the advertiser is paying for the word. It also depends on the placement of the ad. The ads that show on the top of whatever block you are using pay the most for that spot. If someone clicks on that you probably get more. The farther down the listing, the less they are probably paying for the ad.
In using Adsense the idea is to create an site based on a topic that has high paying keywords. You can research this in many different ways. But you also have to know alot about that high paying keyword if you are going to create a website that is successful on that topic.
Popularity: 1% [?]