Ethyl chloride (boiling point, 13 $^{\circ} \mathrm{C}$) is used as a local anesthetic. When the liquid is sprayed on the skin, it cools the skin enough to freeze and numb it. Explain the cooling effect of liquid ethyl chloride.

The enthalpy of vaporization of water is larger than its enthalpy of fusion. Explain why.

Which of the following would result in the more rapid absorption of a drug: a subcutaneous injection or an intradermal injection? Why?

A copper refinery produces a copper ingot weighing 150 lb. If the copper is drawn into wire whose diameter is 7.50 mm, how many feet of copper can be obtained from the ingot? The density of copper is

$$8.94 g/ cm^3$$

(Assume that the wire is a cylinder whose volume

$$V = \pi r ^ { 2 } h$$

where r is its radius and h is its height or length .)

Gold can be hammered into extremely thin sheets called gold leaf. An architect wants to cover a

$$100 \mathrm { ft } \times 82 \mathrm { ft }$$

ceiling with gold leaf that is five-millionths of an inch thick. The density of gold is

$$19.32 \mathrm { g } / \mathrm { cm } ^ { 3 }$$

and gold costs $1654 per troy o unce (1 troy ounce = 31.1034768g). How much will it cost the architect to buy the necessary gold?

The concentration of carbon monoxide in an urban apartment is

$$48 \mu g / m ^ { 3 }$$

What mass of carbon monoxide in grams is present in a room measuring

$$10.6 \mathrm { ft } \times 14.8 \mathrm { ft } \times 20.5 \mathrm { ft } ?$$