Ch. 3

A small birthday candle is weighed, then lighted and placed beneath a metal can containing 100mL of water. Careful records are kept as the temperature of the water rises. Data from this experiment are shown on the graph. What amount of heat energy is released in the burning of candle wax?

0.5 kilocalories per gram of wax burned

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

When an ionic compound such as sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of particles (molecules or ions)?

1 L of 1.0M NaCl

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

10,000 times more

The nutritional information on a cereal box shows that one serving of a dry cereal has 200 kilocalories. If one were to burn one serving of the cereal, the amount of heat given off would be sufficient to raise the temperature of 20kg of water how many degrees Celsius?

10.0°C

One liter of a solution pH 9 has how many more hydroxyl ions (OH⁻) than 1L of a solution of pH 4?

100,000 times more

Equal volumes of vinegar from a freshly-opened bottle are added to each of the following solutions. After complete mixing, which of the mixtures will have the highest pH?

100mL of household cleanser containing 0.5M ammonia

How many grams of the molecule CH3COOH would be required to make 2.5L of a 1M solution of the molecule? (C=12, O=16, H=1)

150

Assume that acid rain has lowered the pH of a particular lake to pH 4.0. What is the hydroxyl ion concentration of this lake?

1x10⁻¹⁰ mol of hydroxyl ion per liter of lake water

How many grams of the molecule CH3COOH would be required to make 1L of a 0.5M solution of the molecule? (C=12, O=16, H=1)

30

At what temperature is water at its densest?

4°C

The molecular weight of water is 18 daltons. What is the molarity of 1 liter of pure water?

55.6M

How many molecules of glucose (C6H2O6 molecular mass = 180 daltons) would be present in one mole of glucose?

6.02E23

How many molecules of glycerol (C3H8O3) would be present in 1L of a 1M glycerol solution?

6.02E23

One mole (mol) of a substance is

6.02E23 molecules of the substance and the molecular mass of the substance expressed in grams

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

6.02E24

You have a freshly-prepared 1M solution of glucose in water. You carefully pour out a 100mL sample of that solution. How many glucose molecules are included in that 100mL sample?

6.02E24

How many grams of the molecule CH3COOH (C=12, O=16, H=1) would be equal to 1 mol of the molecule?

60

You have two beakers. One contains a solution of HCl at pH = 1.0. The other contains a solution of NaOH at pH = 13. Into a third beaker, you slowly and cautiously pour 20 mL of the HCL and 20 mL of the NaOH. After complete stirring, the pH of the mixture will be

7.0

The molecular mass of glucose (C6H12O6) is 180g. Which of the following procedures should you carry out to make a 1M solution of glucose?

Dissolve 180g of glucose in water, and then add more water until the total volume of the solution is 1 L

The molecular mass of glucose (C6H12O6) is 180g. Which of the following procedures should you carry out to make a 0.5M solution of glucose?

Dissolve 90g of glucose in a small volume of water, and then add more water until the total volume of the solution is 1 L

Buffers are substances that help resist shifts in pH by

Donating H⁺ to a solution when they have been depleted and accepting H⁺ when they are in excess

Which of the following ionizes completely in solution and is considered to be a strong acid?

HCl

Why does ice float in liquid water?

Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water

Which of the following takes place as an ice cube cools a drink?

Kinetic energy in the drink decreases

Which of the following statements is completely correct?

NH₃ is a weak base (alkali) and H₂CO₃ is a strong acid

You have two beakers; one contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. You pour crystals of table salt (NaCl) into each beaker. Predict what will happen.

NaCl crystals will dissolve readily in water but will not dissolve in methanol

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

NaOH

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-) and a hydrogen ion (H+). Thus, H2CO3 ↔ HCO3- + H+ If the pH of the blood increases, one would expect

a decrease in the concentration of H2CO3 and an increase in the concentration of H2O

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

a hydrogen bond

Water's high specific heat is mainly a consequence of the

absorption and release of heat when hydrogen bonds break and form

A given solution contains 0.0001 (10⁻⁴) moles of hydrogen ions [H+] per liter. Which of the following best describes this solution?

acidic: H⁺ donor

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. What prediction can we make about the pH of blood as that blood first comes in contact with respiring cells?

blood pH will decrease slightly

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O → H2CO3. Carbonic acid (H2CO3) is a weak acid. If CO2 is bubbled into a beaker containing pure, freshly-distilled water, which of the following graphs correctly describes the results?

c

If the pH of a solution is decreased from 9 to 8, it means that the

concentration of H⁺ has increased 10-fold (10X) compared to what it was at pH9 and concentration of OH⁻ has decreased to one-tenth (1/10) what it was at pH 9

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 than what it was at pH 5

Which of the following solutions has the greatest concentration of hydrogen ions [H⁺]?

gastric juice at pH 2

Identical heat lamps are arranged to shine on identical containers of water and methanol (wood alcohol), so that each liquid absorbs the same amount of energy minute by minute. The covalent bonds of methanol molecules are non-polar, so there are no hydrogen bonds among methanol molecules. Which of the following graphs correctly describes what will happen to the temperature of the water and the methanol?

graph

What gives rise to the cohesiveness of water molecules?

hydrogen bonds

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

hydrogen bonds

A solution contains 0.0000001(10⁻⁷) moles of hydroxyl ions [OH⁻] per liter. Which of the following best describes this solution?

neutral

Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that

none of the other answer choices correctly describes these solutions

Hydrophobic substances such as vegetable oil are

nonpolar substances that repel water molecules

What is the pH of a solution with a hydroxyl ion [OH⁻] concentration of 10⁻¹² M?

pH 2

What is the pH of a solution with a hydrogen ion [H⁺] concentration of 10⁻⁸ M?

pH 8

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

polar covalent bonds

The following question is based on the figure of a solute molecule surrounded by a hydration shell of water. Based on your knowledge of the polarity of water molecules, the solute molecule is most likely

positively charged

Which of the following solutions has the greatest concentration of hydroxyl ions [OH⁻]?

seawater at pH 8

An example of a hydrogen bond is the bond between

the H of one water molecule and the O of another water molecule

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 (HCO₃⁻) and a hydrogen ion (H⁺). Thus, H₂CO₃↔HCO₃⁻+H⁺ If the pH of the blood drops, one would expect

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

Which of the following statements correctly defines a kilocalorie?

the amount of heat required to raise the temperature of 1kg of water by 1°C

Water is able to form hydrogen bonds because

the bonds that hold together the atoms in a water molecule are polar covalent bonds

Pure, freshly-distilled water has a pH of 7. This means that

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

A 100 mL beaker contains 10 mL of NaOH solution at pH = 13. A technician carefully pours into the beaker, 10 mL of HCl at pH = 1. Which of the following statements correctly describes the results of this mixing?

the pH of the beaker's contents falls

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

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

Research indicates that acid precipitation can damage living organisms by

washing away certain mineral ions that help buffer soil solution and are essential nutrients for plant growth