jQuery select option elements by value

I have a select element wrapped by a span element. I am not allowed to use the select id but I am allowed to use the span id. I am trying to write a javascript/jquery function in which the input is a number i, which is one of the values of the select's options. The function will turn the relevant option to selected.

<span id="span_id">
    <select id="h273yrjdfhgsfyiruwyiywer" multiple="multiple">
        <option value="1">cleaning</option>
        <option value="2">food-2</option>
        <option value="3">toilet</option>
        <option value="4">baby</option>
        <option value="6">knick-knacks</option>
        <option value="9">junk-2</option>
        <option value="10">cosmetics</option>
    </select>
</span>

I wrote something as follows (this does not completely work, which is why I am posting this question):

function select_option(i) {

    options = $('#span_id').children('select').children('option');
    //alert(options.length); //7
    //alert(options[0]); //[object HTMLOptionElement]
    //alert(options[0].val()); //not a jquery element
    //alert(options[0].value); //1

    //the following does not seem to work since the elements of options are DOM ones not jquery's
    option = options.find("[value='" + i + "']");
    //alert(option.attr("value")); //undefined
    option.attr('selected', 'selected');

}

Thanks!

Here's the simplest solution with a clear selector:

function select_option(i) {
  return $('span#span_id select option[value="' + i + '"]').html();
}

With jQuery > 1.6.1 should be better to use this syntax:

$('#span_id select option[value="' + some_value + '"]').prop('selected', true);