Calculate the heat, in kilocalories, that is absorbed if 149 g of ice at 0.0 ∘C is placed in an ice bag, melts, and warms to body temperature of 37.0 ∘C. The heat of fusion for water is 80. cal/g, or 334 J/g. The specific heat for water is 1.00 cal/g∘C, or 4.184 J/g∘C.

A quantity of ice at 0C is added to 64.3 g of water in a glass at 55C. After the ice melted, the temperature of the water in the glass was 15C. How much ice was added? The heat of fusion of water is 6.01 kJ/mol and the specific heat is 4.18 J/(g C).

Are changes in state physical or chemical changes? Explain. What type of forces must be overcome to melt or vaporize a substance (are these forces intramolecular or intermolecular)? Define the molar heat of fusion and molar heat of vaporization. Why is the molar heat of vaporization of water so much larger than its molar heat of fusion? Why does the boiling point of a liquid vary with altitude?

A 0.250-g chunk of sodium metal is cautiously dropped into a mixture of 50.0 g water and 50.0 g ice, both at 0C. The reaction is 2Na(s)+2H2O(l)2NaOH(aq)+H2(g)H=368kJ Assuming no heat loss to the surroundings, will the ice melt? Assuming the final mixture has a specific heat capacity of 4.18 J/gc, calculate the final temperature. The enthalpy of fusion for ice is 6.02 kJ/mol.

Explain why 15 g of steam at 100C melts more ice than 15 g of liquid water at 100C.

Will a closed container of water at 70 C or an open container of water at the same temperature cool faster on a cold winter day? Explain why.

Some water is placed in a sealed glass container connected to a vacuum pump (a device used to pump gases from a container), and the pump is turned on. The water appears to boil and then freezes. Explain these changes using the phase diagram for water. What would happen to the ice if the vacuum pump was left on indefinitely?

Consider a substance X with a Hvap = 20.3 kJ/mol and Hfus = 9.0 kJ/mol. The melting point, freezing point, and heat capacities of both the solid and liquid X are identical to those of water. a If you place one beaker containing 50 g of X at 10C and another beaker with 50 g of H2O at 10C on a hot plate and start heating them, which material will reach the boiling point first? b Which of the materials from part a, X or H2O, would completely boil away first? c On a piece of graph paper, draw the heating curve for H2O and X. How do the heating curves reflect your answers from parts a and b?

Liquid butane, C4H10, is stored in cylinders to be used as a fuel. Suppose 35.5 g of butane gas is removed from a cylinder. How much heat must be provided to vaporize this much gas? The heat of vaporization of butane is 21.3 kJ/mol.

A special vessel (see Fig. 10.45) contains ice and supercooled water (both at 10C) connected by vapor space. Describe what happens to the amounts of ice and water as time passes.