Kindly don't just link to online labs. That hardly counts as work on your part. FWIW, I've done gravimetric analysis in an industrial setting, so the setup is pretty trivial to me. If you'd taken the time to paraphrase your procedure for us, you might have been able to answer some of your own questions.
As in your previous question,
http://www.chemicalforums.com/index.php?topic=23221.msg88318#msg88318 there are little to no hints I can give you. Either you've gleaned the basic concepts and specific facts outlined in your analytical chemistry text and class notes, or I'd just end up giving the answers away. For example ...
Why does the precipitate need to be washed?
Why was an excess of barium chloride solution added?
Why must the precipitate be heated to constant mass?
List two reasons why barium sulfate is a suitable product in this gravimetric anaysis?
Can you try to give some ideas for the first three questions? Then, can you combine those answers into the answer for the last one?
Also, i noe the observation part of the prac is usually one of the most easily parts to write, but for this prac i just don't noe wot 2 write. i mean there wasn't that much to observe except for the colour change and weight change, which is already in my results section. Wot do u think i should note? Thanks
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Heh, OK, you also wanted to know why HCl was added to the filtrate. What can you tell us about the properties of chlorides, in general?