Question

what is dry ice what happened when the pressure under which is stored is decreased to atmosphere

Answer 1

dry ice is solidified CO2 . If the pressure in which it is stored, dry ice will turn into CO2 again

Answer 2

dry Ice is actually the solid form of carbon dioxide or co2 and remains at that temperature when the pressure is high and temperature is low.
when the pressure under which it is stored is decreased to atmospheric temperature, dry ice changes into its natural gaseous form...

hope the answer is acceptable.
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