Chapter 3: Thermodynamics

A constant-volume gas thermometer registers an absolute pressure corresponding to 325 mm of mercury when in contact with water at the triple point. What pressure does it read when in contact with water at the normal boiling point?

(a)By how much would the body temperature of the bicyclist in Problem 17.89 increase in an hour if he were unable to get rid of the excess heat? (b) Is this temperature increase large enough to be serious? To find out, how high a fever would it be equivalent to, in °F? (Recall that the normal internal body temperature is 98.6°F and the specific heat of the body is$\mathbf{3480}\mathbf{}\mathbf{J}\mathbf{/}\mathbf{kg}{\mathbf{.}}^{\mathbf{0}}\mathbf{}\mathbf{C}$

The African bombardier beetle (Stenotomus insignis) can emit a jet ofdefensive spray from the movable tip of its abdomen (Fig. P17.91). The beetle’s body has reservoirs containing two chemicals; when the beetle is disturbed, these chemicals combine in a reaction chamber, producing a compound that is warmed from 20ºC to 100ºC by the heat of reaction. The high pressure produced allows the compound to be sprayed out at speeds up to 19 m/s (68 km/h), scaring away predators of all kinds. (The beetle shown in Fig. 1 below is 2 cm long.) Calculate the heat of reaction of the two chemicals (in J/kg). Assume that the specific heat of the chemicals and of the spray is the same as that of water, $\mathbf{4}\mathbf{.}\mathbf{19}\mathbf{\times }\mathbf{10}\mathbf{^}\mathbf{3}\mathbf{\hspace{0.33em}}\mathbf{J}\mathbf{/}\mathbf{kg}\mathbf{\times }\mathbf{K}$, and that the initial temperature of the chemicals is 20ºC.

Fig. 1

In a household hot-water heating system, water is delivered to the radiators at 70.0ºC (158.0ºF) and leaves at 28.0ºC (82.4ºF). The system is to be replaced by a steam system in which steam at atmospheric pressure condenses in the radiators and the condensed steam leaves the radiators at 35.0ºC (95.0ºF). How many kilograms of steam will supply the same heat as was supplied by 1.00 kg of hot water in the first system?

You have 1.50 kg of water at$\mathbf{28}\mathbf{.}\mathbf{0}\mathbf{°}\mathit{C}$in an insulated container of negligible mass. You add 0.600 kg of ice that is initially at$\mathbf{-}\mathbf{22}\mathbf{.}\mathbf{0}\mathbf{°}\mathit{C}$. Assume that no heat exchanges with the surroundings. (a) After thermal equilibrium has been reached, has all of the ice melted? (b) If all of the ice has melted, what is the final temperature of the water in the container? If some ice remains, what is the final temperature of the water in the container, and how much ice remains?

A thirsty nurse cools a 200 - Lbottle of a soft drink (mostly water) by pouring it into a large aluminum mug of mass 0.275 kgand adding 0.120 kgof ice initially at$\mathbf{-}\mathbf{15}\mathbf{.}\mathbf{0}\mathbf{°}\mathit{C}$. If the soft drink and mug are initially at$\mathbf{20}\mathbf{.}\mathbf{0}\mathbf{°}\mathit{C}$, what is the final temperature of the system, assuming that no heat is lost?

A copper calorimeter can with mass 0.446 kgcontains 0.0950 kg of ice. The system is initially at$\mathbf{0}\mathbf{.}\mathbf{0}\mathbf{°}\mathit{C}$. (a) If$\mathbf{0}\mathbf{.}\mathbf{0350}\mathit{k}\mathit{g}$of steam at$\mathit{100}\mathit{.}\mathit{0}\mathit{°}\mathit{C}$and 1.00 atmpressure is added to the can, what is the final temperature of the calorimeter can and its contents? (b) At the final temperature, how many kilograms are there of ice, how many of liquid water, and how many of steam?

A Styrofoam bucket of negligible mass contains 1.75kgof water and 0.450kgof ice. More ice, from a refrigerator at$\mathbf{-}\mathbf{15}\mathbf{.}\mathbf{0}\mathbf{°}\mathit{C}$, is added to the mixture in the bucket, and when thermal equilibrium has been reached, the total mass of ice in the bucket is 0.884 kg. Assuming no heat exchange with the surroundings, what

mass of ice was added?

Question: (a) Which has more atoms: a kilogram of hydrogen or a kilogram of lead? Which has more mass? (b) Which has more atoms: a mole of hydrogen or a mole of lead? Which has more mass? Explain your reasoning.

When a wet cloth is hung up in a hot wind in the desert, it is cooled by evaporation to a temperature that may be$\mathbf{20}\mathbf{}\mathbf{C}\mathbf{°}$or so below that of the air. Discuss this process in light of the second law of thermodynamics.