jquery ul li selector

lucky13

I have this list

<ul style="display:none">
  <li id="key1" title="Look, a tool tip!">item1 with key and tooltip
  <li id="key2" class="selected">item2: selected on init
  <li id="key3" class="folder">Folder with some children
    <ul>
      <li id="key3.1">Sub-item 3.1
      <li id="key3.2">Sub-item 3.2
    </ul>

  <li id="key4" class="expanded">Document with some children (expanded on init)
    <ul>
      <li id="key4.1">Sub-item 4.1
      <li id="key4.2">Sub-item 4.2
    </ul>
</ul>

Is there any way to select each < li > by its “id” with query?

Ive tryed it like this but its now working

$("ul li:#key1").qtip({
         content: '<img src="icons/Icon.png" />'
    });

Thanx for the answers but none of the above was working.. Ive tryed this

$("ul li:first").qtip({
 content: '<img src="icons/Icon.png" />'
});

and im able to see the qtip.But only for the first on the list (key1).
Trying

$("ul li#key1").qtip({
 content: '<img src="icons/Icon.png" />'
});

or

$("#key1").qtip({
 content: '<img src="icons/Icon.png" />'
});

its not working for me.. =/