[jquery] How to remove css property in jQuery

if(prev_clicked)
{   
    $("#accordion li a.category").css('background-image', 'url("img/off_all_channel.png")');                    
    $("#accordion li a.comment").css('background-image', 'url("img/on_all_online.png")');                   
    $(".icha0").removeProperty("background-color");
    $(".icha0").removeProperty("opacity");
}
else
{   
   $(".icha0").css("background-color","#D5D5D2");
   $(".icha0").css("opacity","0.70");
}

I am trying to remove two css properties that I added but It seems not working. Any though?