Dry ice is solid carbon dioxide. Instead of melting, solid carbon dioxide sublimes according to the following equation: CO2( s )→CO2( g ). When dry ice is added to warm water, heat from the water causes the dry ice to sublime more quickly. The evaporating carbon dioxide produces a dense fog often used to create special effects. In a simple dry ice fog machine, dry ice is added to warm water in a Styrofoam cooler. The dry ice produces fog until it evaporates away, or until the water gets too cold to sublime the dry ice quickly enough. Suppose that a small Styrofoam cooler holds 15.0 liters of water heated to 84 ∘C.

Part A:

Use standard enthalpies of formation to calculate the change in enthalpy for dry ice sublimation. (The Δ H ∘ffor CO2(s) is - 427.4kJ/mol).

Express your answer using three significant figures.

Part B:

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 21 ∘C. Assume no heat loss to the surroundings.

Express your answer using two significant figures.