How to detect H₂SO₄ (aq) and NH₃
On mixing 2 parts of $\ce{NH3}$ with 1 part of $\ce{CuCl2}$, following reaction will occur.

$\ce{CuCl2 + 2NH3 -&gt; Cu(NH3)2^{2+} + 2Cl-}$

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 : 

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

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.