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We have two bottle named $\ce{H2SO4~(aq)}$ and solution of $\ce{NH3}$ but we don't know their name actually. What I have to do to detect these solution by only using :

  1. $\ce{CuCl2}$

or

  1. $\ce{NaCO3_{(s)}}$
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  • $\begingroup$ Take two test tubes, add moderate amount of one unknown solution to one of the test tube and the other unknown to another. Add little $NaCO_3$ salt to both of the test tubes. The test tube which gives brisk effervesence was initially filled with $H_2S0_4$, and the other test tube will be having $NH_3$. $\endgroup$ – Immortal Player Nov 5 '13 at 7:23
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On mixing 2 parts of $\ce{NH3}$ with 1 part of $\ce{CuCl2}$, following reaction will occur.

$\ce{CuCl2 + 2NH3 -> Cu(NH3)2^{2+} + 2Cl-}$

This will give you soluble deep-blue copper-ammonia complex: $\ce{Cu(NH3)2^{2+}}$

and also, $\ce{NH3}$ does not react with $\ce{Na2SO4}$.

And $\ce{H2SO4}$ with $\ce{Na2CO3}$ will follow the reaction below :

$\ce{H2SO4_{(aq)} + Na2CO3_{(s)} -> H2O + CO2_{(g)} + Na2SO4_{(aq)}}$

As $\ce{Na2SO4}$ solution is colorless, so you can perform any appropriate test to identify the evolved gas i.e. $\ce{CO2}$.

A simple method used to test $\ce{CO2}$ is :

Bubble the gas through limewater (calcium hydroxide). If carbon dioxide is present, the limewater will turn cloudy and a milky white precipitate will form.

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