Calculate the mass of dry ice that should be added to the water so that the dry ice completely sublimes away when the water reaches 22 ∘
c. assume no heat loss to the surroundings.

15 liters H2O = 15*1000g = 15,000 grams 
heat needed to raise one gram water, one degree celsius = 4.18J 

4.18J * 15,000g = 62,700J = 62.7kJ needed per degree C 

85 - 22 = 63C temp drop needed 

62.7 kJ * 63C = 3950.1kJ needed from CO2 

enthalpy of CO2 = 393.51kJ/mol 
CO2 = 44g/mol = 22.73 moles/kg 
393.51kJ/mol * 22.73 moles/kg 
= 8,943.4 kJ/kg 

3950.1kJ / 8,943.4 kJ/kg = .4417 kg of CO2 needed

That result from subduction of oceanic plates beneath lighter continental plates. most of the earth's volcanoes are located around the pacific ring of fire because that the location of most of the earth's subduction zones.