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Control and Coordination
Acid can be tested in many ways:
i) Test with litmus paper: Place a drop of the given substance on a moist litmus paper. If the colour changes to red, it is an acid.
ii) Test with metals: Acids react with metals to produce salt and hydrogen gas. So if the given substance gives a gas with metals and the gas burns with explosion, then it is acid.
Acid +metal → salt +hydrogen gas
example: 2HCl + Mg → MgCl2 + H2 ↑
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Take 5 ml hydrochloric acid in a boiling tube or a conical flask. Add a few pieces of zinc granules to it.
(a) What do you observe on the surface of zinc granules?
(b) Name the gas evolved.
(c) What happens when the above gas is passed through soap solution?
(d) What happens when a burning candle is brought near the gas filled tube?
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