1)Problem 10.49: Ethyl chloride (boiling point, 13 °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.
Answer: When Ethyl Chloride evaporates, it absorbs the heat from the hand which, in turn, makes the skin cooler.
Problem 10.76: Describe the crystal structure of Pt, which crystallizes with four equivalent metal atoms in a cubic unit cell.
Answer: Unit cells are simple, small, repeating, and have 3 types: simple crib, body-centered, and face-centered.
- Simple cubic-atoms are present at the corners
- Body-centered: atoms are present in the corners and the body center
- Face-centered: atoms are present at the corners and center of each face
In a face-centered unit cell, 1/8 of an atom is present and 1/2 of an atom is present at the center of the face of every cube. The total number of atoms in a front-centered cubic cell is 4. Pt crystallizes with 4 atoms in a unit cell, so the crystal structure is face-centered cubic.
2)10.37- Why does spilled gasoline evaporate more rapidly on a hot day than a cold day?
Answer; When the outside temperature increases, the average kinetic energy of the collective molecules of gasoline increases more quickly because of the weak intermolecular attractions between the molecules, therefore allowing a greater number of molecules to gain sufficient energy to escape from the liquid as vapors.
10.95- As minerals were formed from molten magma, different ions occupied the same cities in the crystals. Lithium often occurs along with Magnesium in minerals despite the different charge of their ions. Suggest an explanation?
Answer: Since the arrangement of atoms in a crystal lattice depends on the size of their cations, and Mg and Lithium have similar size cations, the Mg and Lithium ions can be easily interchanged without altering the structure of the crystals. Mg (2+) and Lithium (1+) often occur together in minerals despite the difference of their charged particles.
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