F4 chem MC

dil HNO3 and dil H2SO4 both are acid, so they react with Na2CO3 to produce CO2 gas.
And CuO is a base, so both acid neutralize the CuO.
But dil HNO3 is an oxidizing agent which will react Cu turnings under heat, but dil H2SO4 has no reaction with Cu turnings even heating since it has no oxidizing power.
So Cu turnings can be used to distinguish between dil HNO3 and dil H2SO4.
The answer is B.

Any ammlnium salt will react with alkaline and produce NH3 gas when heat.
(NH4)2SO4 + 2NaOH --------> 2NH3 + Na2SO4 + 2H2O
Copper ion will react with OH- produce blue ppt but redissolve in excess NaOH
Cu2+ + 2OH- -------> Cu(OH)2 + excess NaOH --------> [Cu(OH)4]2-
Ethanoic acid will neutralize NaOH
The answer is D.

Only carbonate react with nitric acid to produce carbon dixoide gas, but CaCO3 is insoluble in water but Na2CO3 is soluble in water.The other two will not produce any gaseous product with dil nitric acid.
The answer is A.

You should study the last two chapter one more time, as in these chapter it will tell you the ways to test or distinguish the cations or anions. Try harder please.

The person who answered the questions called yuling or something like that has explained in detail. But I want to correct one thing. Cu(OH)2 doesn't dissolve in excess NaOH. Cu2+ ion will form a blue ppt with NH3 and will dissolve in excess NH3 only, forming a complex ion called tetraaminecopper(II) ion.

When you see the question, you should think about what's related to it and actually the questions all hide up some hint. Take the last question as an example. It asks which one is insoluble while producing gas.
You should consider them all which one cannot be dissolved.
Option A is soluble
Option B contains Na+ which is soluble
Option C contains Cl- with Ca2+, which is soluble
Option D contains OH- with Zn2+, which is insoluble

Therefore, you should only consider Option A and Option D

Then you think about which one can produce gas. Option D is a neutralization, therefore no gas is produced but a salt and water, which CO32- produces CO2 with acid, ok?