Question

question 18
which of the following statements is (are) true regarding water? (select all that apply.)
the electrons are in the valence shell of oxygen more than the valence shell of hydrogen.
hydrogen is more electronegative than oxygen.
the oxygen has a partial negative charge and the hydrogen has a partial positive charge.
oxygen is more electronegative than hydrogen.
the electrons are in the valence shell of hydrogen more than the valence shell of oxygen.
the oxygen has a partial negative charge and the hydrogen has a partial positive charge.

question 19
0.5 pts
the liquid found in human stomachs has a ph of 2. therefore, the liquid is a(n) ____?
acid
buffer
isotope
solute
base

question 20
1 pts
the cohesiveness between water molecules is due largely to ______.
hydrogen bonds
their abundance and importance to life
nonpolar ionic bonds
polar ionic bonds
isotopes

Explanation:

Question 18

1. Electronegativity: Oxygen (O) is more electronegative than hydrogen (H). Electronegativity refers to an atom's ability to attract electrons in a covalent bond. Since O is more electronegative, it pulls the shared electrons (in the H - O bonds of water) closer to its valence shell than H. So, the statement "The electrons are in the valence shell of oxygen more than the valence shell of hydrogen" is true. The statement "The electrons are in the valence shell of hydrogen more than the valence shell of oxygen" is false. The statement "Hydrogen is more electronegative than oxygen" is false, and "Oxygen is more electronegative than hydrogen" is true.
2. Partial Charges: Due to the difference in electronegativity, O has a partial negative charge (because it attracts electrons more) and H has a partial positive charge. So the statements "The oxygen has a partial negative charge and the hydrogen has a partial positive charge" (both instances of this statement) are true.

So the true statements are:

• The electrons are in the valence shell of oxygen more than the valence shell of hydrogen.
• The oxygen has a partial negative charge and the hydrogen has a partial positive charge. (first instance)
• Oxygen is more electronegative than hydrogen.
• The oxygen has a partial negative charge and the hydrogen has a partial positive charge. (second instance)

The pH scale ranges from 0 - 14. A pH less than 7 indicates an acid, a pH of 7 is neutral, and a pH greater than 7 indicates a base. A buffer is a solution that resists changes in pH. An isotope is a variant of an element with a different number of neutrons. A solute is a substance dissolved in a solvent. Since the stomach liquid has a pH of 2 (which is less than 7), it is an acid.

1. Cohesion in water: Cohesion is the attraction between molecules of the same substance. In water, cohesion is largely due to hydrogen bonds. Water molecules are polar, with O having a partial negative charge and H having a partial positive charge. The partially positive H of one water molecule is attracted to the partially negative O of another water molecule, forming hydrogen bonds.
2. Eliminating other options:

• "Their abundance and importance to life" is not related to the cause of cohesiveness.
• Water has polar covalent bonds, not nonpolar ionic bonds (ionic bonds involve the transfer of electrons, and water's bonds are covalent).
• Water has polar covalent bonds, not polar ionic bonds.
• Isotopes are related to the number of neutrons in an atom, not to molecular cohesion.

Answer:

• The electrons are in the valence shell of oxygen more than the valence shell of hydrogen.
• The oxygen has a partial negative charge and the hydrogen has a partial positive charge. (first occurrence)
• Oxygen is more electronegative than hydrogen.
• The oxygen has a partial negative charge and the hydrogen has a partial positive charge. (second occurrence)

Question 19