Chapter 2

Why is water considered a polar molecule? A. The oxygen is found between the two hydrogens. B. The oxygen atom attracts the hydrogen atoms. C. The oxygen end of the molecule has a slight negative charge, and the hydrogen end has a slight positive charge. D. Both hydrogens are at one end of the molecule, and oxygen is at the other end.

C. The oxygen end of the molecule has a slight negative charge, and the hydrogen end has a slight positive charge.

Which of the following elements, essential to life, is a trace element? A. phosphorus B. carbon C. iodine D. calcium

C. iodine

An atom with an electrical charge is a(n. ______. A. isotope B. molecule C. ion D. compound

C. ion

An uncharged atom of gold has an atomic number of 79 and an atomic mass of 197. This atom has ______ protons, ______ neutrons, and ______ electrons. A. 79... 118... 79 B. 118... 79... 118 C. 118... 276... 118 D. 79... 34... 79

A. 79... 118... 79

What name is given to substances that resist changes in pH? A. buffers B. sugars C. salts D. bases

A. buffers

The bond between oppositely charged ions is a(n. ______ bond. A. ionic B. polar C. hydrogen D. covalent

A. ionic

Relative to a pH of 6, a pH of 4 has a ______. A. 200 times higher H+ concentration B. 100 times higher H+ concentration C. 20 times higher H+ concentration D. 100 times lower H+ concentration

B. 100 times higher H+ concentration

The lower the pH of a solution, the ______. A. greater the number of oxygen atoms B. more acidic the solution C. less toxic the solution D. higher the OH— concentration

B. more acidic the solution

All atoms of an element have the same number of ______. A. protons plus neutrons B. protons C. electrons D. neutrons

B. protons

Beryllium's atomic mass is 9 and its atomic number is 4. How many neutrons are found in a beryllium atom? A. 9 B. 13 C. 4 D. 5

D. 5