Displacement activity

I wanted to see if I could create a picture by reacting aluminium foil with a solution of copper (II) chloride made at home.

The idea was to scratch the surface of the aluminium foil with a stainless steel sewing needle, thus removing the surface oxide layer and exposing the metal underneath in an etched pattern. I hoped the exposed metal would then react preferentially in a displacement reaction when brought into contact with a solution of copper (II) chloride. I envisaged that copper would be deposited at the scratched areas, ‘painting’ a picture in copper so to speak, on the surface of the aluminium foil. However, things did not turn out quite as I had expected, as can be seen in the series of images below.

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Take 15cm of thin copper wire and about 25ml of bathroom cleaner containing 13% hydrochloric acid

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Put the copper wire into the bathroom cleaner

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Leave them to react – here is what it looked after 1 day

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After about 2 days the copper had dissolved producing an acidic solution of green copper (II) chloride on the right

At this stage I scratched a pattern into the bottom of an aluminium foil pie dish, as can be seen in the picture above on the left.

I wanted the aluminium to react with the copper (II) chloride producing copper and aluminium chloride. However, the copper (II) chloride solution was still very acidic and I should have predicted what happened next.

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A vigorous exothermic reaction took place, with lots of bubbles of colourless gas produced

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The gas produced during the reaction created a foam with the surfactants in the bathroom cleaner – seen here after about 2 minutes

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It was all over after a few minutes with the base of the pie dish completely eaten away

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Plenty of copper metal had been produced as predicted – seen here after washing with water

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The morning after

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No etched image, although I did get the copper back

At least three chemical reactions took place in the above displacement activity.

Write balanced chemical equations for these reactions:

  1. copper metal + hydrochloric acid
  2. aluminium + copper (II) chloride solution
  3. aluminium + hydrochloric acid

Answers next time.

 

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