How to pass multiple parameters in json format to a web service using jquery

$.ajax({
    type: "POST",
    url: url,
    data: "{'Id1':'2'}",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: callback
});

$.ajax({
    type: "POST",
    url: url,
    data: "{'Id1':'2'},{'Id2':'2'}",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: callback
});

data: "{'Ids':[{'Id1':'2'},{'Id2':'2'}]}"

data: "{'Ids':['2','2']}"