Review Quiz Ch. 2

Use the words and phrases below to correctly complete the paragraph on buffers. Labels may be used more than once or not at all.

A buffer is a chemical solution that keeps pH within normal limits by absorbing excess hydrogen, or H+, ions and hydroxide, or OH-, ions. In humans, our blood pH is about 7.4. If the blood pH drops below this number, acidosis occurs and if the blood pH rises above this number, alkalosis occurs. Both of these conditions can be harmful to humans. pH stability in blood is achieved through a built-in buffer. When hydrogen ions are added to blood, a reaction occurs to reduce acidity and no significant change in pH is observed as a result. When hydroxide ions are added to blood, a reaction occurs to reduce basidity and no significant change in pH is observed as a result.

Complete the following statements using the pH scale provided when necessary.

The pH scale ranges from 0 to 14 and is used to indicate the alkalinity of a solution. A solution with a(n) neutral pH has a(n) equal number of H⁺ and OH⁻ ions. In both directions on the scale, between the whole number value, there is a difference of ten times the concentration of hydrogen ions and hydroxide ions. A pH of 5 is 100 times more acidic than a pH of 7. Sea water, which has a pH of 8, has a higher concentration of OH⁻ than urine, which has a pH of 6. There is one thousand times as much OH⁻ in household ammonia as there is in seawater.

Fill in the blanks below to describe the different types of chemical bonds.

Hydrogen bonds occur when partially positive hydrogen atoms attract partially negative atoms nearby. Examples include the attraction between two molecules of water. Ionic bonds occur when atoms are held together by an attraction between negatively and positively charged ions. Examples include NaCl and MgCl₂. Single covalent bonds occur when one pair of electrons is shared between the outer shells of two atoms. Examples include the bond between 2 hydrogen atoms. Double covalent bonds occur when two pairs of electrons are shared between the outer shells of two atoms. Examples include the bond between 2 oxygen atoms. Triple covalent bonds occur when three pairs of electrons are shared between the outer shells of two atoms. Examples include the bond between 2 nitrogen atoms.

For each of the following scenarios, label with the correct pH. Then, place each scenario in order from highest H+ concentration to lowest H+ concentration from top to bottom.

If the hydrogen ion concentration is 1x10⁻³ , the pH is 3. If the hydrogen ion concentration is 0.00001, the pH is 5. If the hydrogen ion concentration is 0.00000001, the pH is 8. If the hydroxide ion concentration is 0.00001, the pH is 9. If the hydroxide ion concentration is 0.001, the pH is 11. If the hydrogen ion concentration is 1x10⁻¹³ , the pH is 13.

Complete the paragraph to describe how the properties of water assist in transport within organisms.

The ability of water molecules to cling to each other is referred to as cohesion. This clinging ability is due to the fact that water molecules are held together by hydrogen bonds. Most organisms contain vessels that utilize this function of water in order to transport nutrients and wastes. In plants, vessels are used to help move the water throughout from the root to the leaves. When moving through the vessels in plants, adhesion also keeps the water attached to the vessels for movement.

Complete the following paragraph to correctly describe how water associates in solution.

Due to water's polarity, it is capable of dissolving a great number of substances. A solution contains a dissolved substance called a solute. In a mixture of salt water, salt is the solute, water is the solvent, and salt water is the solution. When salt is added to water, the negative poles of the water molecules are attracted to the positive sodium ions, and the positive poles of the water molecule are attracted to the negative chloride ions. The result is that the sodium and chloride ions dissociate in water.

Hydrogen bonds form between individual water molecules and contribute to the many unique properties of water. The following video describes hydrogen bonds and how they are formed. Watch the video and then answer the questions that follow. A polar covalent bond can best be described as:

a bond where electrons are unequally shared, resulting in more electrons orbiting certain atoms than others.