Question

A few pieces of dry ice, CO2(s), at -78°C are placed in a flask that contains air at 21°C. The flask is sealed by placing an uninflated balloon over the mouth of the flask. As the balloon inflates, the dry ice disappears and no liquid is observed in the flask.
State the direction of heat flow that occurs between the dry ice and the air in the flask.

Answer 1

The dry ice absorbs heat from the air in the flask and become CO2 gas directly. So the heat flow from air to dry ice. And the CO2 gas increase the amount of the air. Though the temperature decreases, the balloon still inflates.