A 3.0-kg block of lead is taken from a furnace at $300^{\circ} \mathrm{C}$ and placed on a large block of ice at $0{ }^{\circ} \mathrm{C}$. The specific heat of lead is $0.13 \mathrm{~J} / \mathrm{g}{ }^{\circ} \mathrm{C}$. If all the heat given up by the lead is used to melt ice, how much ice is melted when the temperature of the lead drops to $0{ }^{\circ} \mathrm{C}$ ? $(10.5)$

Draw the electron-dot formula for each of the following molecules or ions: a. $\mathrm{HCCH}$ (ethyne) b. $\mathrm{CS}_2$ c. $\mathrm{NO}^{+}$

How many kilojoules are released when $75.0 \mathrm{~g}$ of steam at $100{ }^{\circ} \mathrm{C}$ condenses, cools to $0^{\circ} \mathrm{C}$, and freezes? (Hint: The solution will require three energy calculations.)

Draw the electron-dot formula for $\mathrm{Cl}_2 \mathrm{O}$.

Determine the total number of valence electrons for each of the following: a. $\mathrm{H}_2 \mathrm{~S}$ b. $\mathrm{I}_2$ c. $\mathrm{CCl}_4$ d. $\mathrm{OH}^{-}$

A homeowner is considering these heating systems for heating his house: Electric resistance heating with $0.12/ kWh and 1 kWh = 3600 kJ, gas heating with$1.24/therm and 1 therm = 105,500 kJ, and oil heating with $2.3/gal and 1 gal of oil = 138,500 kJ. Assuming efficiencies of 100 percent for the electric furnace and 87 percent for the gas and oil furnaces, determine the heating system with the lowest energy cost.

A homeowner is considering these heating systems for heating his house: Electric resistance heating with $\$ 0.09 / \mathrm{kWh}$ and $1 \mathrm{kWh}=3600 \mathrm{~kJ}$, gas heating with $\$ 1.24 /$ therm and 1 therm $=105,500 \mathrm{~kJ}$, and oil heating with $\$ 1.25 / \mathrm{gal}$ and $1 \mathrm{gal}$ of oil $=138,500 \mathrm{~kJ}$. Assuming efficiencies of $100$ percent for the electric furnace and $87$ percent for the gas and oil furnaces, find the heating system with the lowest energy cost.

Death Valley holds the record for the highest recorded temperature in the United States. On July 10, 1913, at a place called Furnace Creek Ranch, the temperature rose to $134 ^ { \circ } \mathrm { F }$. The lowest U.S. temperature ever recorded occurred at Prospect Creek Camp in Alaska on January 23, 1971, when the temperature plummeted to $- 79.8 ^ { \circ }$. Convert the Celsius temperatures to Kelvin.

Sugaring season in Vermont is going full blast. Vermont, the biggest U.S. syrup producer, produces about 500,000 gallons a year. In 2007, maple syrup cost an average of $35 a gallon; this year, the price is$45 a gallon. Canada is usually a huge producer, but with a poor season it has seen a 30 percent drop in production. As consumers turn to natural and organic products and buy locally made food, demand for maple syrup has rocketed.

Draw a graph to describe the maple syrup market and the cost and revenue of one firm in 2007, assuming that all firms are making zero economic profit.

A homeowner is considering these heating systems for heating his house: Electric resistance heating with $\$ 0.09 / \mathrm{kWh}$ and $1 \mathrm{~kWh}=3600 \mathrm{~kJ}$, gas heating with $\$ 1.24 /$ therm and 1 therm $=105,500 \mathrm{~kJ}$, and oil heating with $\$ 1.25 / \mathrm{gal}$ and $1 \mathrm{~gal}$ of oil $=138,500 \mathrm{~kJ}$. Assuming efficiencies of $100$ percent for the electric furnace and $87$ percent for the gas and oil furnaces, Find the heating system with the lowest energy cost.

The ultimate analysis of a No. 4 fuel oil is 86.47 wt% carbon, 11.65% hydrogen, 1.35% sulfur, and the balance noncombustible inerts. This oil is burned in a steam-generating furnace with 15% excess air. The air is preheated to $175^{\circ} \mathrm{C}$ and enters the furnace at a gauge pressure of 180 mm Hg. The sulfur and hydrogen in the fuel are completely oxidized to $\mathrm{SO}_{2} \text { and } \mathrm{H}_{2} \mathrm{O}$; 5% of the carbon is oxidized to CO, and the balance forms $\mathrm{CO}_{2}$. a) Calculate the feed ratio $\left(\mathrm{m}^{3} \text { air }\right) /(\mathrm{kg} \text { oil })$. b) Calculate the mole fractions (dry basis) and ppm (parts per million on a wet basis, or moles contained in $10^{6}$ moles of the wet stack gas) of the stack-gas species that might be considered environmental hazards.

The $4 \mathrm{m} \times 4 \mathrm{m}$ horizontal roof of an uninsulated aluminum melting furnace is comprised of a 0.08-m-thick fireclay brick refractory covered by a 5-mm-thick steel (AISI 1010) plate. The refractory surface exposed to the furnace gases is maintained at 1700 K during operation, while the outer surface of the steel is exposed to the air and walls of a large room at $25^{\circ} \mathrm{C}$. The emissivity of the steel is $\varepsilon=0.3$. (a) What is the rate of heat loss from the roof? (b) If a 20-mm-thick layer of alumina-silica insulation $\left(64 \mathrm{kg} / \mathrm{m}^{3}\right)$ is placed between the refractory and the steel, what is the new rate of heat loss from the roof? What is the temperature at the inner surface of the insulation? (c) One of the process engineers claims that the temperature at the inner surface of the insulation found in part (b) is too high for safe, long-term operation. What thickness of fireclay brick would reduce this temperature to 1350 K?

Suppose that it is $70^{\circ} \mathrm{F}$ in your house when the furnace breaks down at midnight. The outside temperature is $10^{\circ} F.$ You notice that after 30 minutes the inside temperature has dropped to $50^{\circ} \mathrm{F}.$ (a) What will the temperature be after one hour (that is, at 1:00 AM)? (b) How long will it take for the temperature to drop to $15^{\circ} \mathrm{F}$