Bio Chapter 2-3
A small birthday candle is weighed, then lighted and placed beneath a metal can containing 100 mL 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?
.5 kilocalories per gram of wax burned
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 solute particles (molecules or ions)?
1 L of 1 M NaCl
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?
1 x 10-10 mol of hydroxyl ion per liter
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 20 kg of water how many degrees Celsius?
10 degrees
One liter of a solution of pH 2 has how many more hydrogen ions (H+) than 1 L of a solution of pH 6?
10,000 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?
100 mL of household cleanser
One liter of a solution of pH 9 has how many more hydroxyl ions (OH-) than 1 L of a solution of pH 4?
100,000 times more
From its atomic number of 15, it is possible to predict that the phosphorus atom has
15 protons and 15 electrons
What is the maximum number of covalent bonds an element with atomic number of 8 can make with hydrogen?
2
What is the maximum number of electrons in a 2p orbital of an atom?
2
What is the valence of an atom with six electrons in its outer shell?
2
A molecule of carbon dioxide (CO2) is formed when one atom of carbon (atomic number 6) is covalently bonded with two atoms of oxygen (atomic number 8). What is the total number of electrons that must be shared between the carbon atom and the oxygen atoms in order to complete the outer electron shell of all three atoms?
4
The molecular weight of water is 18 daltons. What is the molarity of 1 L of water?
55.6 M
You have a freshly prepared 0.1 M glucose solution. Each liter of this solution contains how many glucose molecules?
6.02 x 10 24
You have a freshly prepared 1M solution of glucose in water. You carefully pour out a 100 mL sample of that solution. How many glucose molecules are included in that 100 mL sample?
6.02 x 10 24
How many grams of the molecule in figure 3.2 would be equal to 1 mole of the molecule?
60
A group of molecular biologists is trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone?
A compound with the same three dimensional shape as part of the hormone
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
Which results from the unequal sharing of electrons between atoms?
A polar covalent bond
A given solution contains .0001(10-4) moles of hydrogen ions per liter. Which of the following best describes this solution?
Acidic, H+ donor.
Which of the following is true for this reaction? 3H2 + N2 = 2NH3
Ammonia is being formed and decomposed
Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a possible result is that
An electron may move to an electron shell farther out from the nucleus
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
About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?
Carbon, hydrogen, nitrogen, oxygen
The molecular mass of glucose is 180 g. Which of the following procedures should you carry out to make a 1 M solution of glucose.
Dissolve 180 g of glucose in water and then add more water until the total volume of the solution is 1 L.
Nitrogen (N) is much more electronegative than hydrogen (H). Which of the following statements is correct about the atoms in ammonia (NH3)?
Each hydrogen atom has a partial positive charge
Which of the following best describes chemical equilibrium?
Forward and reverse reactions continue with no effect on the concentrations of the reactants and products.
Which of the following solutions has the greatest concentration of hydrogen ions?
Gastric juice at pH 2
If an atom of sulfur (atomic number 16) were allowed to react with atoms of hydrogen (atomic number 1), which of the molecules below would be formed?
H S H
The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound.
H2S
Which of the following ionizes completely in solution and is considered to be a strong acid.
HCl
Which of the following explains most specifically the attraction of water molecules to one another?
Hydrogen bond
Which type of bond must be broken for water to vaporize?
Hydrogen bonds
Why does ice float in liquid water?
Hydrogen bonds stabilize and keep the molecules of ice farther apart that the water molecules of liquid water.
Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by humans and other vertebrates?
Iodine
Which of the following results from a transfer of electrons between atoms?
Ionic bond
The atomic number of neon is 10. Therefore, which of the following is correct about an atom of neon?
It has 8 electrons in its outer shell and it is inert
The atomic number of chlorine is 17. The atomic number of magnesium is 12. What is the formula for magnesium chloride?
MgCl2
Which of the following statements is completely correct?
NH3 is a weak base, and HCl is a strong acid.
In ammonium chloride salt (NH4Cl) the anion is a single chloride ion, Cl. What is the cation of NH4Cl?
NH4 with a charge of +1
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?
NaOH
A given solution contains .0000001(10-7) moles of hydroxyl ions per liter. Which of the following best describes this solution?
Neutral
When two atoms are equally electronegative, they will interact to form
Non polar covalent bonds
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 answer choices correctly describes these solutions
Many mammals control their body temperature by sweating. Which property of water is most directly responsible for the ability of sweat to lower body temperature?
The absorption of heat by the breaking of hydrogen bonds
In the term trace element, the modifier trace means
The element is required in very small amounts
Which of the following describes any reaction that has reached chemical equilibrium?
The rate of the forward reaction is equal to the rate of the reverse reaction.
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.
If the pH of the blood increases, one would expect
a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3-
Water's high specific heat is mainly a consequence of the
absorption and release of heat when hydrogen bonds break and form
Atoms whose outer electron shells contain eight electrons tend to
be stable and chemically non-reactive
If the pH of a solution is decreased from 9 to 8, it means that the
concentration of H+ has increased to 10-fold compared to what it was a 9 pH, and concentration of OH- has decreased to one-tenth compared to what it was a 9 pH
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 it was at pH 5
Buffers are substances that help reist shifts in pH by
donating H+ to a solution and accepting H+ when they are in excess
Van der Waals interactions result when
electrons are not symmetrically distributed in a molecule
One mole of a substance is
its molecular weight in grams and 6.02 x 10 23 molecules
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 concentration of 10-8 M?
pH 8
Based on your knowledge of the polarity of water molecules, the solute molecule is most likely
positively charged
An example of a hydrogen bond is the bond between
the H of one water molecule and the O of another water molecule
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
Water is able to form hydrogen bonds because
the bonds that hold together the atoms in a water molecule are polar covalent bonds
The reactivity of an atom arises from
the existence of unpaired electrons in the valence shell
A van der Waals interaction is the weak attraction between
the nucleus of one molecule and the electrons of a nearby molecule
