Ch. 3 Pearson Practice Test
Temperature Moderation (2)
-Temperature: measures the average kinetic energy of a substance. - Heat energy: takes into account the amount of matter that is at a certain temperature. *Temperature and heat energy are different. Water has high specific heat [ 1 cal/ g *C] which helps moderate air or body temperature. Water has high heat of vaporization which helps with evaporative cooling.
27. A mole of ethyl alcohol weighs 46 g. How many grams of ethyl alcohol are needed to produce 1 L of a 2-millimolar (2 mM) solution?
0.092 g
4 emergent properties of water
1. Cohesion (+adhesion, + surface tension) 2. Temperature moderation 3. Insulation 4. Solvent
32. A solution at pH 6 contains __________ than the same amount of solution at pH 8.
100 times more H+
25. Why are cell membranes composed primarily of hydrophobic molecules?
In order to perform their function of separating the aqueous solutions outside cells from the aqueous solutions inside cells, cell membranes cannot be soluble in water.
11. Adhesion is best described as which of the following?
The clinging of one substance to another substance
9. The ability of water molecules to form hydrogen bonds with other water molecules and water's ability to dissolve substances that have charges or partial charges are __________.
both caused by water's partial charges
24. A molecule that has all nonpolar covalent bonds would be __________.
hydrophobic
18. Sweating has a cooling effect because of water's high __________.
heat of vaporization
29. Adding acid tends to __________ of a solution.
increase the hydrogen ion concentration and lower the pH
Buffer
A solution that contains a weak acid and its corresponding base. A buffer minimizes changes in pH when acids or bases are added to the solution. Ex) Carbonic acid and bicarbonate ion maintain near neutral pH of blood (pH 7.4) H2CO3 --- HCO3 + (H+) If substance becomes too acidic move left. If substance becomes too basic move right.
8. What do cohesion, surface tension, and adhesion have in common with reference to water?
All are properties related to hydrogen bonding.
1. Cells are surrounded by water, with which they are mostly filled. Which of the following occurs as a result?
All of the listed responses are correct.
22. How does the polarity of water contribute to its ability to dissolve so many substances?
Because it is polar, water's negatively charged oxygen atoms and positively charged hydrogen atoms are attracted to positively and negatively charged ions and molecules.
23. What are nonpolar molecules that cluster away from water molecules called?
Hydrophobic
13. Which action would involve the greatest transfer of heat?
Condensing 5 g of steam to liquid water
30. Which of the following dissociations is that of an acid?
HF → (H+) + (F-)
5. Which of the following accurately relates the emergent properties of water to the effects of global warming in the Arctic?
Ice floats because it is less dense than liquid water; floating ice insulates water below and provides a habitat for some species. The significant increase in Arctic air temperature over the past 50 years is causing a reduction in sea ice, compromising these beneficial effects of sea ice.
20. Which of the following occurs because molecules of water are farther apart in ice than in liquid water?
Ice floats.
Order of solubility in water (most to least)
Ionic bonds (b/c of their strong charge) Polar Covalent bonds Non polar covalent bonds *Water likes charged molecules
35. Why is the increasing amount of carbon dioxide being taken up by the oceans a cause for concern?
More carbon dioxide causes an increase in carbonic acid (H2CO3), which leads to a decrease in the concentration of carbonate ion (CO32-).
Insulation (3)
Since ice is less dense than liquid water, it will rest on top and insulate liquid water below it.
12. You can fill a glass of water to just slightly above the rim without the water spilling over the glass. What property of water best explains this phenomenon?
Surface tension
14. Imagine that organisms consisted of 70-95% alcohol instead of 70-95% water. Alcohol's specific heat is about half that of water. How would living things be different?
Systems for temperature regulation would have to be much more efficient.
2. Water is a polar molecule. What does this statement mean?
That atoms in the molecule have partial charges as a result of unequal sharing of electrons in a covalent bond
6. If water were not a polar molecule, how would the effects of climatic warming differ from those currently observed or predicted to occur in the future?
The effects would be drastically worse because the loss of the polar nature of water would greatly reduce its specific heat and its ability to moderate temperature.
4. In a group of water molecules, hydrogen bonds form between which of the following?
The oxygen atom in one water molecule and a hydrogen atom in another water molecule
Adhesion (1)
Water molecules sticking to other surfaces.
28. An acid is __________.
a compound that donates hydrogen ions to a solution
19. Water has __________ than other liquids such as ethanol, reflecting its capacity to absorb large amounts of heat.
a higher boiling point
34. A substance that minimizes changes in the concentration of H+ and OH- in a solution is a __________.
buffer
10. The phenomenon responsible for maintaining the upward movement of water through vessels in a tree is __________.
cohesion
36. The absorption of human-generated CO2 by the oceans __________.
increases the hydrogen ion concentration in the oceans but decreases the carbonate ion concentration and threatens the livability of the oceans for organisms that produce calcium carbonate shells
Mole
is a quantity. =6(10^23) = mass (g)/molar mass
7. The tendency of water molecules to stay close to each other as a result of hydrogen bonding __________.
is called cohesion, acts to moderate temperature, provides the surface tension that allows small animals to move across a water surface, and helps to keep water moving through the vessels in a tree trunk
17. The reason that coastal climates are more moderate than inland climates primarily water's high __________.
specific heat
33. Adding a base tends to __________ of a solution.
lower the hydrogen ion concentration and increase the pH
21. Water is a very versatile solvent because water molecules are __________.
polar
Molarity
refers to the concentration of a solution using number of moles of solute per liter of water = moles/ liters
Surface Tension (1)
relates to strength of cohesion. (surface bonds are stronger)
26. Sucrose has a molecular mass of 342 daltons. To make a 2-molar (2 M) solution of sucrose, __________.
stir 342 g of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 0.5 L
31. A glass of grapefruit juice, at pH 3, contains __________ H+ as a glass of tomato juice, at pH 4.
ten times as much
16. The amount of heat required to convert 1 g of any substance from the liquid to the gaseous state is defined as __________.
the heat of vaporization of that substance
15. The amount of heat required to change the temperature of 1 g of any substance by 1°C is defined as __________.
the specific heat of that substance
3. The partial charges on a water molecule occur because of __________.
the unequal sharing of electrons between the hydrogen and the oxygen atoms of a water molecule
Water as a solvent (4)
water is a powerful solvent because of its polarity.
Cohesion (1)
water molecules stick to each other because of hydrogen bonding.
