Compare Elements via jQuery

I'm in a situation where I want to check if two elements (one is clicked and another one a reference) are the same, what I'm trying to do is:

$("#process li").click(function() {
   currentElement = $(this);
   referenceElement = $("#process li:first-child");
   if (currentElement === referenceElement) {
        $(".mark").removeClass("mark");
        $(this).addClass("mark");
   }
});

So what I want is to check if the clicked <li> is the first child of the ul#process and if so first remove a .mark class from another element and then add it to the clicked one. I don't get any working result - ideas anyone?