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letter 33308
What causes vinegar to form less rust
than water?
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Hello, thank you for listening. I'v read these questions and
answers and none of them have told me anything I need to find out
about my project that I'm doing. So far none of he questions or
answers have anythingto do with what I'm about to ask. Why is the
vinegar the one that causes less rust on the nail than the water. I
know every thing about the oxidation and how that plays a major part
in the water being the one that causes the more rust but, why does
the vinegar the one that causes the least rust. I really don't get it
because I've researched it and I still don't get it and the quetions
and answers here haven't helped me a bit so I was wondering if u
could help me out a little bit more. Is there something in the
vinegar that causes less rust to form or what? please help try to get
back to me a.s.a.p. thank you very much!
Mar I.
science project - Staten Island , New York
First of two simultaneous responses -- ++++
Mar,
You spent a lot of time telling us what you know, but not much on
what you're doing. So I'll make some assumptions. You had two
completely identical nails. You poured some vinegar into a container
and covered a nail. You did the same with some tap water.
It's hard to say for sure, without seeing your setup and being
able to measure things, why you got more rust on the water nail,
because all else being equal one would expect a more acidic solution
to have a higher corrosion rate. However, the tap water probably had
a lot of dissolved oxygen and the vinegar would have less. Most
faucets aerate the water that comes out. Oxygen is crucial to the
reactions that include the dissolution of iron, or of zinc if your
nails were galvanized (meaning coated with zinc).
The electrons generated when iron corrodes have to go somewhere,
and that somewhere is usually a reaction including oxygen. Depending
on how full the containers were when you started, whether they were
protected from or open to the atmosphere, the ease of getting oxygen
into the solution would have varied. Hope that this helps some. You
could try things over with water that has been boiled and then cooled
without agitation, which will reduce its oxygen content. Also make
sure that the nails are identical and have been cleaned identically.
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Paul Tibbals,
P.E.
gas & electric
San Ramon, CA, USA
(My opinions are not related to nor a
statement of my employer's)
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Second of two simultaneous responses -- ++++
I'm impressed you know everything about oxidation! I know lots of
people who know they don't know as much about it as they would like,
so perhaps they can ask you!! Seriously, the reason vinegar doesn't
rust as much as water is because vinegar is acidic (acetic acid) and
this dissolves the metal, along with its oxides, leaving a clean
surface. Since the salts it produces dissolve in the vinegar, you
often don't easily see them. On the other hand, water is not so
acidic, so it corrodes, or rusts, the metal to form an oxide or
hydroxide; with iron, this usually appears as a brown mess. To prove
the point take two samples of iron and weigh them. Then put one of
them into water and the other into vinegar. Leave the for a week and
take them out. Carefully wash and dry them and then re-weigh them.
Tell us what you find.
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Trevor Crichton
R&D practical scientist - UK
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