When carbon(1v)oxide is passed through calcium hydroxide solution for a short time a white precipitate is formed, but when passes through sodium hydroxide, no precipitate is formed explain

It is Calcium Carbonate. CaCO3.

Interestingly, Calcium Carbonate is available in the natural form in mines and is called limestone. So, in order to put it to good use, you need to convert it to quick lime (CaO) which is done by calcining(heating) the limestone at about 850 degrees Celsius. This releases carbon dioxide.

CaCO3 --heat--> CaO + CO2

The above reaction is , of course, the stoichiometric representation and the actual process produces CO as by product and the oxygen that is used for combustion is also a part of the gas phase.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.