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<p>[QUOTE=&quot;-jeffB, post: 1371272, member: 27832&quot;]I&#039;m afraid your teacher had it backwards, as you found out. Experiments always win. <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie1" alt=":)" unselectable="on" unselectable="on" /></p><p><br /></p><p><a href="http://chemistry.about.com/od/chartstables/a/Activity-Series-Of-Metals.htm" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://chemistry.about.com/od/chartstables/a/Activity-Series-Of-Metals.htm" rel="nofollow">http://chemistry.about.com/od/chartstables/a/Activity-Series-Of-Metals.htm</a></p><p><br /></p><p>This chart is a <i>general</i> guide; it won&#039;t always tell you everything. For example, hydrochloric acid won&#039;t normally attack copper, but if the copper is already <i>oxidized</i>, the acid will dissolve the oxide layer. And if there&#039;s oxygen dissolved in the water, you can get further oxidation. The end result is that the copper goes away, despite what the table says.</p><p><br /></p><p>Zinc, on the other hand, goes <i>fast</i> when you hit it with almost any kind of acid. Being in contact with the copper actually makes the zinc dissolve even faster! It also protects the copper from further attack while this is happening. It&#039;s the same principle as <a href="http://en.wikipedia.org/wiki/Galvanization" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://en.wikipedia.org/wiki/Galvanization" rel="nofollow">galvanization</a>, except that putting the zinc on the <i>inside</i> is, well, kind of dumb.</p><p><br /></p><p>Nitric acid is both an acid and an oxidizer; it&#039;ll dissolve copper pretty quickly. If it&#039;s concentrated enough, it&#039;ll give off clouds of brown, heavy, and extremely toxic nitrogen dioxide; don&#039;t try this at home. (In fact, it&#039;s best to avoid nitric acid in general.) It&#039;s no use using it to try to &quot;de-plate&quot; the copper off a zincoln; once it gets through to the zinc in one spot, the zinc will go, faster than the copper.</p><p><br /></p><p>It&#039;s pretty common knowledge that vinegar (dilute acetic acid) will &quot;restore dates&quot; on Buffalo nickels -- for reasons I don&#039;t fully understand, the date and other features don&#039;t dissolve as quickly as the fields, and so dissolving a thin layer from the entire coin tends to bring those features out. When I forgot and left a few in vinegar (in a closed container!) for several months, I was surprised to find them copper-colored -- I suppose the vinegar preferentially attacked the nickel from the alloy (see the chart above), leaving the copper behind. Try it with a nickel from your pocket change if you&#039;re curious. (Don&#039;t do too many, though -- nickel salts, formed when the nickel dissolves, aren&#039;t great for the environment.)</p><p><br /></p><p>Can you tell that I think chemistry is fun? <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie1" alt=":)" unselectable="on" unselectable="on" />[/QUOTE]</p><p><br /></p>

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