Homework: Ch. 3 Water and Life

Which type of bond must be broken for water to evaporate?

Hydrogen bonds

A strong acid like HCI

Ionizes completely in aqueous solution

Which of the following statements is true about buffer solutions?

They maintain a relatively constant pH when either acids or bases are added to them

A dietary Calorie equals 1 kilocalorie. Which of the following statements correctly defines 1 kilocalorie?

1,000 calories, or the amounts of heat required to raise the temperature of 1 kg of water by 1°C

One liter of a solution of pH 2 has how many more hydrogen ions (H+) than 1 Liter of a solution of pH 6?

10,000 times more

One liter of a solution of pH 9 has how many more hydroxyl ions (OH-) that 1 Liter of a solution of pH 4?

100,000 times more

What is the hydrogen ion (H+) concentration of a solution of pH 8?

10⁻⁸ M

You have a freshly prepared 0.1 M of glucose in water. Each liter of this solution contains how many glucose molecules?

6.02x10²²

How many molecules of glycerol (C8H8O3; molecular mass= 92) would be present in 1 L of a 1 M glycerol solution?

6.02x10²³

One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that, when placed in an aqueous solution, dissociates into a bicarbonate ion (HCO3-3) and i hydrogen ion (H+). Thus,

A decrease in the concentration of H2CO3 and an increase in the concentration of HCO₃⁻

Which of the following effects is produced by the high surface tension of water?

A water strider can walk across the surface of a small pond

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2+H2O<--> H2CO3. Carbonic acid (H2CO3) is a weak acid. Respiring cells release CO2 into the bloodstream. What will be the effect of pH of blood as that blood first comes in contact with respiting cells?

Blood pH will decrease slightly.

Buffers are substances that help resist shifts in pH by?

Both donating H+ from a solution when bases are added, and accepting H+ when acids are added

Why does ice float in liquid water?

Hydrogen bonds stabilize and keep the molecules of ice further apart that the water molecules of liquid water

A 0.01 M solution of a substance has a pH of 2. What can you conclude about this substance?

It is a strong acid that ionizes completely in water.

Which of the following ionizes completely in solution and is considered to be a strong base (alkali)?

NaOH

A solution contains 0.0000001 (10 to the negative 7th power) moles of hydroxyl ions (-OH) per liter. Which of the following best describes this solution?

Neutral

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by?

Polar Covalent bonds

If a solution has a pH of 7, this means that?

The concentration of H+ ions in the water equals the concentration of OH- ions in water.

The partial negative charge in a molecule of water occurs because?

The electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus

Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?

The release of heat by the formation of hydrogen bonds

The slightest negative charge at one end of one water molecule is attracted to the slightest positive charge of another water molecule. What is that attraction called?

a hydrogen bond

Liquid water's high specific heat is mainly a consequence of the

absorption and release of heat when hydrogen bonds break and form.

Water molecules are able to form hydrogen bonds with

compounds that have polar covalent bonds

If the pH of a solution is increased from pH 5 to pH 7, it means that the

concentration of OH- is 100 times greater that what it was at pH 5

Which of the following solutions would require the greatest amount of base to be added to bring the solution to neutral pH?

gastric juice at pH 2

Hydrophobic substances such as vegetable oil are

non-polar substances that repel water molecules

What is the pH of 1 millimolar NaOH solution?

pH 11

What is the pH of a solution with a hydroxyl ion (OH-) concentration of 10 to the negative 12th power M?

pH²

One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO-3) and a hydrogen ion (H+). Thus, Formula on worksheet If the pH of the blood drops would expect?

the HCO3⁻ to act as a base and remove excess H+ with formation of H2CO3