Chapter 2 SmartBook Bio 181
When an acid is dissolved in water, how does it change the solution's pH?
It decreases the solution's pH by releasing protons in the solution.
What is true of a molecule of gaseous hydrogen (H2)?
It has no net charge.
Solid water is _________ dense than liquid water.
less
If a solution has a pH of 3, then its hydrogen ion concentration is which of the following?
1 x 10-3 M
No orbital can contain more than
2 electrons
Water has a high heat of vaporization because it takes a large amount of energy to do which of the following?
Break the hydrogen bonds between different water molecules
Which of the following molecules is likely to have the highest specific heat and the highest heat of vaporization?
H2O
Identify the four most abundant elements in living organisms.
Carbon Nitrogen Oxygen Hydrogen
In structural formulas, each solid line between atomic symbols represents a single _____________bond.
Covalent
Typically, as the temperature increases, what happens to the rate of a chemical reaction?
It also increases.
A dalton is a unit of which of the following?
Mass
Electrons that are farther from the nucleus always have which of the following?
More potential energy
Can a catalyst change the equilibrium of a reaction?
No
Electrons with the same potential energy always occupy which of the following
The same energy level
Hydrophobic exclusion refers to which of the following?
The tendency of non-polar molecules to clump together in water
The crystal of the ionic compound NaCl is composed of
a matrix of ions with a precise geometry.
--------atoms usually have no neutrons.
protium
An atom has 11 protons, 12 neutrons, and 10 electrons. This atom has an atomic number of ______, an atomic mass of ______, and an overall charge of ______.
*11; 23; +1* 11; 23; +1 11; 12; +1 23; 12; +1
What is the charge of a hydroxide ion?
-1
Molecules that are more polar tend to have which of the following characteristics?
-A higher heat of vaporization -A higher specific heat
Which of the following statements are true?
-Most enzymes in living systems are extremely sensitive to pH. -It is important for cells to maintain a fairly constant pH. -Even small changes in pH can alter the shape of enzymes and other proteins.
If you dissolve 0.05 mol of sugar into 100 ml of water, the result is which of the following? 0.5 M solution of sugar 0.05 M solution of sugar Reason: The capital M indicates molarity, which is given as mol/L. If you dissolve 0.05 mol in 100 ml, you will have the equivalent of 0.5 mol in a liter (10x100ml=1L). Therefore, the resulting solution is 0.5 M. 0.005 M solution of sugar Reason: The capital M indicates molarity, which is given as mol/L. If you dissolve 0.05 mol in 100 ml, you will have the equivalent of 0.5 mol in a liter (10x100ml=1L). Therefore, the resulting solution is 0.5 M.
0.5 M solution of sugar
Why is solid water less dense than liquid water?
As the movement of water molecules slows down when liquid water changes to ice, hydrogen bonds form that space the molecules relatively far apart.
In a neutral atom, the number of electrons is equal to which of the following?
The atomic number
The surface tension of water is due to which of the following? The low density of liquid water The high specific heat of water The adhesion of water molecules The cohesion of water molecules
The cohesion of water molecules
These two diagrams each represent a molecule of which of the following? Ammonia Methane Water Carbon dioxide
Water
When 1 g of fructose is dissolved in 500 mL of water, __________is the solvent and ___________________ is the solute.
Water Fructose
Which of the following explains why water rises inside a capillary glass tube?
Water molecules adhere to the surface of the glass.
Which of the following accurately describes the cause of the high surface tension of water?
Water molecules attract each other.
The number and configuration of electrons determines an element's
chemical properties
What shape do p orbitals have?
dumbbell
In living systems, ionic compounds generally exist as
individual ions.
Chemical bonds that form due to the attraction between oppositely charged atoms that have gained or lost electrons are called____________ bonds.
ionic
By determining the ratio of the different ___________of carbon and other elements in a sample, scientists are able to accurately determine the age of the sample.
isotopes
Carbon-12, carbon-13, and carbon-14 are examples of different
isotopes
Scientists often need to follow specific molecules and their progress either in a chemical reaction or in living cells and tissues. In such studies, radioactive isotopes can be used to
label the molecules.
Electron __________represent probability distributions for electrons, that is, regions surrounding the nucleus where there is the highest probability of finding electrons.
orbitals
An atom participating in a chemical reaction loses one or more electrons. The process of losing an electron in a reaction is called
oxidation
A___________covalent bond is formed by an unequal sharing of one or more electron pairs.
polar
When the pH of a solution falls by 2, the [H+] is reduced in half. Reason: if the pH falls by 2, the [H+] increases 100-fold the [H+] doubles. Reason: if the pH falls by 2, the [H+] increases 100-fold the [H+] increases 100-fold. the [H+] rises by 2. Reason: if the pH falls by 2, the [H+] increases 100-fold the [H+] increases 10-fold. Reason: if the pH falls by 2, the [H+] increases 100-fold
the [H+] increases 100-fold.
True or false: Electrons are found in the atom's nucleus
*False* True Reason: Protons and neutrons comprise the atom's nucleus; electrons are found in orbitals.
Select the molecules that tend to be hydrophobic.
-Oils -Nonpolar molecules -Hydrocarbon chains (chains composed entirely of carbon and hydrogen atoms)
Select the molecules that tend to be hydrophilic.
-Polar molecules Reason: Polar molecules have partial charges so they are attracted to water and are hydrophilic. -Ions Reason: Ions have charges so they are attracted to water. and are hydrophilic.
Which of the following statements about nonpolar molecules are true? They have regions of partial positive charge and regions of partial negative charge. The distribution of electrical charge is uniform Some can form hydrogen bonds with polar molecules. They are electrically neutral
-The distribution of electrical charge is uniform -They are electrically neutral
Match each subatomic particle with its electrical charge.
0 neutron +1 proton -1 electron
If a solution has a pH of 3, then its hydrogen ion concentration is which of the following? 1 x 103 M 1 x 10-3 M 1 x 10-3 Reason: This answer does not have units - it could mean anything, for example number of protons. The equation for pH is only valid if the concentration of protons is expressed in terms of molar concentration. 3 x 103 M 1 x 103
1 x 10-3 M
Arrange the following states of water in order from most dense to least dense (start with most dense at the top).
1.Liquid 2.Solid 3.Gas
The angle between the two O-H covalent bonds in a molecule of water is how many degrees (to the tenth place)?
104.5
The angle between the two bonds that hold a water molecule together is approximately which of the following?
104.5 degrees
An electrically neutral atom has an atomic number of 11 and an atomic mass of 23. This atom has ________protons, _______neutrons, and _________ electrons.
11,12,11
If an atom has 6 electrons in its outermost layer, how many covalent bonds must it form in order to have a stable outer shell of electrons?
2
A molar concentration of 2 M is equal to:
2 mol/L
In a single covalent bond, _________ electrons are shared (please enter the number of shared electrons).
2 or two
This question refers to elements in the main groups of the periodic table. According to the octet rule, if an atom's first energy level is the outermost shell then it is stable with __________electrons and if an atom has any other energy level as its outermost shell then it is stable with _______electrons.
2,8
An element has five electrons in its outer shell. As such, it needs how many electrons to fill its outer energy level?
3 4 Reason: For most of the atoms important for life, the outermost energy level contains 8 electrons when full. 2 Reason: For most of the atoms important for life, the outermost energy level contains 8 electrons when full. 1 Reason: For most of the atoms important for life, the outermost energy level contains 8 electrons when full. 5 Reason: For most of the atoms important for life, the outermost energy level contains 8 electrons when full.
If an atom has 4 electrons in its outermost energy level, how many covalent bonds must it form in order to have a stable outer shell of electrons?
4
In a double covalent bond, ____________total electrons are shared (please only enter the number of shared electrons).
4
Which of the following bonds involves the sharing of one or more pairs of electrons?
A covalent bond
How does the partial charge of a polar covalent bond compare to the unit charge of an ion?
A partial charges is far smaller than a unit of charge
Which of the following is the strongest bond?
A triple covalent bond
By determining the ratio of the different isotopes of carbon in a sample, scientists are able to accurately determine which information about the sample?
Age
What do we call a substance that cannot be broken down into simpler substances by ordinary chemical means?
An element
A chlorine atom that has gained an electron and has an overall negative charge is an example of which of the following?
Anion
Which of the following best describes the entire acidic range of the pH scale?
Any pH value below 7
Why does water have very high specific heat?
Because a large input of thermal energy is required to break the many hydrogen bonds between individual water molecules.
This graph illustrates the titration of a solution with base. The buffering range of this solution can best be described as which of the following? Between pH 4 and pH 6 Below pH 4 Between 1X and 4X Reason: Buffering range is described in terms of pH not in term of how much acid or base is added because the latter will vary depending on the strength of the acid or base. Above pH 6 Above pH 6 and below pH 4
Between pH 4 and pH 6
When an acid is added to the blood, how does the carbonic acid/bicarbonate buffer work to stabilize pH?
Bicarbonate removes H+ from the blood.
What do we call the ability of water to rise inside a tube of narrow diameter against the pull of gravity?
Capillary action
Because polar water molecules attract each other, water is said to be
Cohesive
For any given isotope, such as C-14, the rate of decay can be described as which of the following?
Constant
Atomic mass is measured in which of the following units?
Daltons (Da)
Redox reactions involve a transfer of _________ from one atom to another.
Electrons
The number and configuration of ______ determines the chemical behavior of an atom.
Electrons
Order the following atoms in increasing order of their electronegativity, starting at the top with the least electronegative one.
H C N O
The stronger an acid is, the higher its concentration of ______ ions and the lower its concentration of ______ ions.
H+; OH-
Stronger bases have lower concentrations of ______ ions and therefore have a ______ pH.
H+; higher
Which of the following are molecular formulas?
H2 O2
Select the polar molecule.
H2O
It takes a large amount of heat energy to break ________bonds between water molecules; this explains why water has a very _________heat of vaporization.
Hydrogen High
Within an atom, where are electrons found?
In orbitals that surround the nucleus
Regarding ionic compounds, which is more often found in living systems?
Individual ions dissolved in water
Deficiency for which trace element can lead to an enlargement of the thyroid gland and the formation of a goiter?
Iodine
As the concentration of reactants increases, so do the collisions between them, which causes which of the following?
It speeds up the chemical reaction.
Isotopes are atoms of the same element that differ in the number of which of the following?
Neutrons
What type of bond forms between 2 identical atoms?
Nonpolar covalent
Water tends to repel or exclude which of the following?
Nonpolar molecules Hydrophobic molecules
Almost all the mass of an atom is located in which of the following?
Nucleus
Different isotopes of an element behave the same way chemically because they have the same number of which of the following?
Number of electrons
Which of the following are structural formulas?
O=O H—H
Which of the following atoms has the highest electronegativity? Carbon Hydrogen Oxygen Nitrogen
Oxygen
A hydrogen bond can form between the partially negative___________ atom of one water molecule and the partially positive____________atom of another water molecule.
Oxygen Hydrogen
Substances or a mixture of substances known as buffers, act in living things to resist changes in
PH
The negative logarithm of the hydrogen ion concentration of a solution is known as its
PH
The ___________charges produced by a polar covalent bond are much smaller than the unit charge of an ion.
Partial
Which bond is formed by an unequal sharing of one or more electron pairs?
Polar covalent
Which two particles are the primary determinants of an element's atomic mass?
Protons Neutrons
Which of the following defines isotopes that are unstable and tend to break apart into elements with lower atomic numbers while releasing a significant amount of energy?
Radioactive
If two atoms are joined by a polar covalent bond, the shared electrons will tend to stay closer to the atom with which of the following characteristic?
The higher electronegativity
During capillary action, the water will rise higher in which situation?
The narrower the capillary tube is
Why does the rate of a reaction increase as the concentration of reactants increases? The reactants move slower. Reason: Lowering the temperature causes the reactants to move slower, not increasing the concentration. The reactants move faster. Reason: Raising the temperature causes the reactants to move faster, not increasing the concentration. The reactants collide with each other less frequently. The reactants collide with each other more frequently.
The reactants collide with each other more frequently.
What is the half-life of an isotope?
The time it takes for one-half of the radioactive isotope atoms in a sample to decay.
Arrange the following bonds in order from strongest to weakest. Start with the strongest at the top.
Triple Covalent Double Covalent Single Covalent Hydrogen
The molecule shown in these two diagrams is held together by which of the following bonds?
Two single polar covalent bonds
Electrons in outer, unfilled energy levels are known as ________________ electrons.
Valence
How is the arrangement of water molecules related to its density?
Water molecules in ice are locked into a crystal-like lattice due to hydrogen bonds, making ice less dense than liquid.
A substance that increases [H+] and decreases pH when it dissociates in water is called a(n)____________
acid
If a person's pH has a value of 7.1, that person is said to exhibit
acidosis
The attraction of water to other polar substances is called___________
adhesion
Electrons in the same energy level
always have the same potential energy
Atoms with a net negative charge are known as _______,whereas atoms with a net positive charge are known as
anions cations
A substance that decreases [H+] and increases pH when it dissociates in water is called a(n)
base
An(n) ___________is a substance or a mixture of substances that act to resist changes in pH.
buffer
The ability of water to rise inside a tube of narrow diameter against the pull of gravity is called_______ action
capillary
Organic molecules are relatively complex molecules that contain a backbone of ______________ atoms
carbon
A(n)_____________is any substance that increases the rate of a reaction without being altered itself.
catalyst
Valence electrons and their interactions determine the ______________properties of an element.
chemical
Chemical bonds are broken and new bonds are formed during a(n)
chemical reaction
Most multicellular organisms maintain the pH of the fluid surrounding cells at values that are
close to neutral
Match each type of bond or interaction with its description.
covalent bond>>>> matches Choice, sharing of electrons ionic bond>>> matches Choice, attraction between oppositely charged atoms hydrogen bond>>>> matches Choice, attraction between a covalently bound H atom with a slight positive charge and another covalently bound atom with a slight negative charge hydrophobic interaction>>>>>> matches Choice, nonpolar regions of a molecule are forced together in order to minimize contact with water molecules van der Waals attraction>>>>>>> matches Choice, weak attraction between atoms due to oppositely polarized electron clouds
True, discrete molecules form when atoms are connected by
covalent bonds
Atoms differ in their affinity for ___________neutrons , a property called electronegativity.
electrons
Subatomic particles called -----can be found at various distances from the nucleus (please only write the name of the particle without specifying its charge or other properties).
electrons
A substance that cannot be broken down into simpler substances by ordinary chemical means is called a(n)
element
When electrons move closer to the nucleus,
energy is released.
The letters K, L, M, and so on are used to designate different
energy levels in an atom
The stronger an acid is, the ______ its concentration of hydrogen ions and the ______ its pH.
higher; lower
When a sugar crystal is placed in water, every time a sucrose molecule dissociates from the crystal, water molecules surround it in a cloud forming a(n) ____________shell that prevents it from associating with other sucrose molecules.
hydration
--------atoms always have one proton.
hydrogen
The relatively weak, but numerous __________bonds that form between a water molecule and other molecules (including other water molecules) play a key role in determining the properties of water (please spell the name of the bonds, no abbreviations).
hydrogen
The tendency of nonpolar molecules to aggregate together in water is known as _____________ exclusion.
hydrophobic
A catalyst is any substance that _____________ the rate of a reaction without being altered itself.
increases
Fish and other animals can survive at the bottom of a lake during winter because ice is _____________dense than liquid water.
less
When writing out structural formulas, covalent bonds are represented by solid ___________between atomic symbols.
lines
The stronger a base is, the ______ its concentration of hydrogen ions and the ______ its pH.
lower; higher
A(n) _________ , is made of two or more atoms held together by chemical bonds in a stable association. The atoms may or may not belong to the same element.
molecule
Isotopes differ in the number of________ they contain.
neutrons
A(n)__________ , covalent bond involves an equal sharing of one or more pairs of electrons.
nonpolar
Almost all the mass of an atom is located in the
nucleus
Atoms are composed of a central ------which is surrounded by orbiting --------
nucleus electrons or electron cloud
If two atoms are joined by a polar covalent bond, the atom with the lower electronegativity will have a partial __________charge.
positive
Atomic number refers to the number of ----------in an atom. Atomic number refers to the number of which of the following?
protons
Atoms of the same element always have the same number of protons , --------in the nucleus, and this number is unique for that element.
protons
The three main types of subatomic particles are-------- --------- ----------
protons neutrons electrons
Within an atom, ______ and ______ have nearly equal masses, while ______ have a much smaller mass.
protons; neutrons; electrons
By convention, when writing a chemical equation the ________are listed on the left side of the arrow and the_________are listed on the right side of the arrow.
reactant products
During a chemical reaction, the substances we start out with are called ________substances we end up with are called______________
reactants products
An atom participating in a chemical reaction gains one or more electrons. The process of gaining electrons in a reaction is called
reduction
Buffers stabilize the pH of solutions by ______ hydrogen ions when a base is added and ______ hydrogen ions when an acid is added.
releasing; absorbing
When 1 g of sugar is dissolved in 500 mL of water, the sugar is called the ___________and water is called the _______________.
solute solvent
The amount of heat 1 g of a substance must absorb or lose to change its temperature by 1°C is called
specific heat
All atoms are composed of several types of------- protons , Incorrect Unavailable particles. A proton is an example of such a particle.
subatomic
The property of ________ __________is a measure of how difficult it is to stretch or break the surface of a liquid.
surface tension
The Blank 1 of 1 of a substance is a measure of how rapidly its individual molecules are moving.
temperature
The pH of a solution is defined as
the negative logarithm of the hydrogen ion concentration in the solution.
A(n) ________________molecule can break apart to form a positive hydrogen ion and a negative hydroxide ion.
water or H2O
The green sphere in the simple "Bohr model" of atoms shown here represents which of the following?
*An electron* An orbital A proton An energy level A neutron Reason: The atom on the left has one tan sphere and no purple spheres in the nucleus. Therefore, tan must represent protons and purple neutrons because all atoms must have at least one proton.
In the diagram, the 2 black circles (marked with two arrows) surrounding the large green sphere represent which of the following (choose all that apply)?
*Electron shells Electron energy levels* The nucleus Reason: the large green sphere in the center represents the nucleus
If an atom gains or loses electrons, it is known as which of the following?
*Ion* Isotope Anion Reason: This term describes an atom that has gained electrons but not an atom that has lost electrons. Cation Reason: This term describes an atom that has lost electrons but not an atom that has gained electrons.
In the simple "Bohr model" of atoms shown here, the tan spheres represent which of the following?
*Protons* Electrons Daltons Orbitals
Which of the following are subatomic particles?
*Protons* *Electrons* *Neutrons* Orbitals Reason: orbitals refer to the volume of space where electrons are most likely to be found Ions Reason: ions are atoms or molecules that have gained or lost electrons
Which subatomic particles are located in the nucleus of an atom (choose all that apply)?
*Protons* *Neutrons* Electrons Reason: Electrons are found in orbitals surrounding the nucleus. ions Reason: Ions are atoms that have lost or gained one or more electrons.
Which of the following (choose all that apply) correctly describe electrons within atoms?
*They occupy discrete energy levels.* They follow a specific path or orbit as they move around the nucleus. Reason: Electrons don't follow a path. They occupy a space around the nucleus (called an orbital) with a certain probability. They cannot move from one energy level to another. Reason: If an electron receives an input of energy, it can move to a more distant energy level. Similarly, an electron can move to an orbital that is closer to the nucleus and, in the process, release energy.
If two atoms have the same number of protons in their nucleus, you can conclude for sure that they
*are atoms of the same element* are the same isotope Reason: Just because two atoms have the same number of protons in their nucleus, does not mean they are the same isotope. They could have different numbers of neutrons, which would make them two different isotopes of the same element. have the same atomic mass Reason: Just because two atoms have the same number of protons in their nucleus, does not mean they have the same atomic mass. They could have different numbers of neutrons, which would make them have different atomic masses.
Atoms are composed of a central -------,which is surrounded by orbiting
*nucleus* *electrons*
Atoms of different chemical elements can be differentiated based on the number of-----
*protons in the nucleus* electrons in all shells electrons in the outermost shell Reason: Although the number of electrons matches the number of protons in uncharged atoms, the number of electrons varies in ions. The identify of the element is based on the number of protons. orbitals in the outermost shell neutrons in the nucleus Reason: Elements are identified based on the number of protons they contain. The number of neutrons is used to distinguish different isotopes of the same element from one another.
A hydrogen ion, formed during the dissociation of water, has a charge of which of the following? -1 Reason: Atoms become ions when they lose or gain electrons. The hydrogen atom has 1 electron. When water releases a hydrogen ion, it is always a hydrogen atom that has lost an electron (the electron stays with the oxygen, producing OH-). -2 +2 Reason: A hydrogen atom cannot have a charge of 2+, because it only has one proton (so its maximum charge is +1). In order for an ion to be 2+, it would have to have two protons at least, i.e. it would have to be an element other than hydrogen.
+1
Ionic bonds involve which of the following? (choose all that apply)
-A transfer of electrons from one atom to another -An attraction between atoms with opposite electrical charges
Rank the following bonds and interactions in order from strongest to weakest starting with the strongest at the top. When ranking the bonds, assume that they occur in a biological system, i.e. chemical compounds are dissolved in water.
-Covalent bond -Ionic bond -Hydrogen bond -Hydrophobic interaction -Van der Waals attraction
How are enzymes in cells affected by changes in pH?
-Even small changes in pH can alter the shape of enzymes and other proteins and affect their ability to function.
Select the reasons that the molecule formed by two hydrogen atoms (H2) is stable.
-It has no unpaired electrons. -It has no net charge. -It is held together by a covalent bond.
An electrically neutral atom has an atomic number of 6 and an atomic mass of 14. This atom has ___________protons, ______neutrons, and _____________electrons.
6,8,6
The pH inside most cells and of the fluid surrounding the cells of multicellular organisms is fairly close to which pH?
7
Which of the following is the neutral point of the pH scale?
7
The neutral point of the pH scale is
7 or 7.0
An atom has 8 protons, 9 neutrons, and 8 electrons. This atom has an atomic number of ______, an atomic mass of ______, and an overall charge of ______.
8; 17; 0
If a solution has a [H+] of 10-9 M, then its pH is
9
If a solution has a [H+] of 10-9 M, then its pH is __________________ Please only fill in with the actual, specific value (a number) of the pH in this case.
9 or nine
The defining feature of organic compounds is the presence of which of the following?
A backbone of carbon atoms
How do catalysts work?
A catalyst shortens the time needed to reach equilibrium.
Which of the following best describes the entire alkaline range of the pH scale? pH values between 6 and 14 Reason: pH values below 7 are acidic. Any pH value above 7 pH values between 7 and 13 Reason: pH values above 13 are also alkaline, for example, a pH of 13.3 is considered alkaline. pH values between 8 and 14 Reason: pH values above 7 and below 8 are also alkaline, for example, a pH of 7.3 is considered alkaline.
Any pH value above 7
Which of the following best describes how temperature affects the rate of a chemical reaction (assume care has been taken that the temperature is not too high as to destroy the reactants)? As temperature increases, the reaction rate first increases and then decreases. Reason: This is only true in certain cases, for example when the reaction is catalyzed by an enzyme. As temperature increases, the reaction rate decreases. Reason: Unless the temperature is so high that the reactant molecules are destroyed, as the temperature increases, so does the rate of the reaction. As temperature increases, the reaction rate increases. As temperature increases, the reaction rate first decreases and then increases. Reason: Unless the temperature is so high that the reactant molecules are destroyed, as the temperature increases, so does the rate of the reaction.
As temperature increases, the reaction rate decreases. Reason: Unless the temperature is so high that the reactant molecules are destroyed, as the temperature increases, so does the rate of the reaction.
Explain why the organic substance C2H5OH is considered a compound?
Because it contains molecules made of atoms of different elements
Which of the following occurs because solid water is less dense than liquid water (choose all that apply)?
Bodies of water freeze from the top down. Ice floats. Aquatic organisms can survive in liquid water below the frozen surface of ponds and lakes.
This graph illustrates the titration of a solution with base. Consider the behavior of the solution in the pH range of 4-6. In this range, this solution can best be described as which of the following? Buffered A base Reason: Since the solution resists changes in pH between pH 4 and pH 6, it acts as a buffer in this range Neutral Reason: Since the solution resists changes in pH between pH 4 and pH 6, it acts as a buffer in this range An acid Reason: Since the solution resists changes in pH between pH 4 and pH 6, it acts as a buffer in this range Unbuffered Reason: Since the solution resists changes in pH between pH 4 and pH 6, it acts as a buffer in this range
Buffered
Which property of water is best illustrated by this diagram? Solubility of polar substances High heat of vaporization Capillary action Expansion of water as it freezes High specific heat
Capillary action
Which of the following are compounds?
Carbon dioxide Water Sodium chloride
The key buffer in human blood is an acid-base pair consisting of______________ acid and ________________
Carbonic bicarbonate
What are the two components of the key buffering system in human blood?
Carbonic acid Bicarbonate
When a base is added to the blood, how does the carbonic acid/bicarbonate buffer work to stabilize pH?
Carbonic acid releases H+ into the blood.
A sodium atom that has lost an electron and has an overall positive charge is an example of which of the following?
Cation
Valence electrons and their interactions determine the ________ properties of an element.
Chemical
A chemical reaction involves the breaking and formation of
Chemical bonds
Match each property of water with how it benefits life.
Correct Answer -cohesion>>>>> matches Choice, plant leaves pull water up from the roots -high specific heat matches Choice, water stabilizes the temperature of organisms and the environment -high heat of vaporization matches Choice, organisms sweat or pant to cool themselves matches Choice, many types of ions and molecules move freely in cells, permitting a diverse array of chemical reactions -water is less dense as a solid than as a liquid matches Choice, aquatic organisms can survive below the frozen surface of ponds and lakes
Water consists of one oxygen atom joined to two hydrogen atoms by two single, polar _______________ bonds.
Covalent
Water consists of one oxygen atom joined to two hydrogen atoms by what type of bonds?
Covalent
What type of bond is formed when 2 atoms share one or more pairs of valence electrons?
Covalent
How does the decay rate of different radioactive isotopes compare?
Different radioactive isotopes decay at different rates.
How do ions in a crystal matrix interact?
Each ion is attracted to all of the oppositely charged ions in its vicinity
The volume of space around the nucleus where an electron is most likely to be found is known as which of the following?
Electron orbital
In the diagram, the purple shapes represent which of the following?
Electron orbitals
The affinity of an atom for an electron is also known as which of the following?
Electronegativity
It takes work to keep electrons in their orbitals due to which of the following?
Electrons are attracted to the nucleus.
Anything that has mass and occupies space is defined as which of the following?
Energy Atomic Weight *Matter*
The letters K, L, M, and so on are used to designate which of the following?
Energy levels
In order for an electron to move to a more distal orbital which of the following must occur?
Energy must be added
In living systems, which of the following catalyze almost every chemical reaction necessary for life?
Enzyme
In living organisms, almost all chemical reactions are catalyzed by protein catalysts called
Enzymes
The rate of decay for a radioactive isotope is usually expressed using which of the following?
Half-life
The amount of energy required to change 1 g of a substance from a liquid to a gas is called which of the following?
Heat of vaporization
What is the temperature of a substance a measure of?
How fast its molecules are moving
The attraction between the partially negative oxygen atom of one water molecule and the partially positive hydrogen atom of another water molecule is called a(n) ______ bond. hydrogen ionic Reason: Ionic bonds occur between ions, which are atoms that have gained or lost one or more electrons. polar covalent Reason: In a covalent bond two atoms share a pair of electrons. This is not the case here, where a small positive charge is attracted to a small negative charge. This bond occurs between two water molecules without any sharing of electrons. covalent Reason: In this weak bond there is no sharing of electrons. Therefore this bond is not considered a covalent bond.
Hydrogen
Water has a high specific heat because a large input of thermal energy is needed to break the many __________ ____________ that restrict the movement of individual water molecules.
Hydrogen bonds
Substances that attract water are called ___________("water-loving") while substances that repel water are called _________("water-fearing").
Hydrophilic Hydrophobic
Water tends to repel or exclude ____________ molecules.
Hydrophobic
Consider a large protein molecule that has some parts that are highly hydrophobic. When placed in a water solution, the protein folds in a globular shape, such that all the hydrophobic portions are inside the molecules, away from water. This is an example of which of the following?
Hydrophobic exclusion
Which property of water strongly affects the overall shape of many biological molecules, such as protein, and DNA?
Hydrophobic exclusion
Of the following list of bonds and interactions, which one is the weakest?
Hydrophobic interaction
The atoms in NaCl are held together by what type of bond?
Ionic
Unlike ______ bonds, which produce a crystal lattice, __________ bonds are formed between 2 individual atoms, giving rise to true, discrete molecules.
Ionic Covalent
How are ions formed?
Ions are formed when atoms lose or gain one or more electrons.
How does water's high specific heat affect living organisms?
It helps prevent organisms from overheating due to the thermal energy released by chemical reactions inside cells. It helps organisms maintain a relatively stable internal temperature when the external temperature rises or falls.
What does it mean when we say water is adhesive? It is held together by strong covalent bonds. It is attracted to each other. Reason: The property of water molecules to attract each other is called cohesion. It is attracted to nonpolar molecules. It is attracted to other polar molecules and ions.
It is attracted to other polar molecules and ions
Electrons are attracted to the positive charge of the nucleus, therefore, which of the following is true?
It takes work to keep them in their orbitals.
Electrons that are closer to the nucleus always have which of the following?
Less potential energy
During radioactive decay, an atom typically breaks up into elements with which of the following?
Lower atomic numbers
How does water's high heat of vaporization affect living organisms? The temperature of dry air tends to fluctuate more than the temperature of humid air. Reason: This statement is true, but it is due to the high specific heat of water. Many organisms sweat or pant in order to cool themselves. When your body is wet, you feel cooler than when your body is dry. Organisms that live in water generally experience a more stable environmental temperature than organisms that live on land. Reason: This statement is true, but it is due to the high specific heat of water.
Many organisms sweat or pant in order to cool themselves. When your body is wet, you feel cooler than when your body is dry.
Anything that has mass and occupies space is defined as
Matter
A group of atoms held together by chemical bonds in a stable association is called which of the following?
Molecule
Atoms are composed of which of the following?
Molecules Ions Macromolecules *Subatomic particles*
Compared to covalent bonds, hydrogen bonds are which of the following? About the same, but slightly stronger Much stronger Much weaker About the same, but not stronger
Much weaker
Which of the following molecules are nonpolar?
N2 O2 CH4 Reason: although C and H differ slightly in electronegativity, the difference is negligible and C-H bonds are considered nonpolar
Water carries two partial ___________charges on the oxygen atom and two partial _________charges, one on each hydrogen atom.
Negative Positive
A single water molecule can spontaneously break apart (ionize) to form which of the following? Two positive ions (one hydrogen and one hydroxide) Two negative hydroxide ions and 2 positive hydrogen ions One positive hydrogen ion and one negative hydroxide ion Two positive hydrogen ions and one negative hydroxide ion
One positive hydrogen ion and one negative hydroxide ion
How is the crystal structure of salt formed?
Positively charged sodium ions are attracted to negatively charged chloride ions.
Atoms are composed of a central nucleus which is surrounded by which orbiting particles?
Protons *Electrons* Ions Neutrons
Among subatomic particles, each _______has a charge of +1, each ______has a charge of -1, and each ________has no charge.
Protons Electrons Neutrons
The atomic mass of an atom is equal to the sum of the masses of its
Protons and neutrons
Which subatomic particles determine the atomic mass of an atom?
Protons and neutrons
Different isotopes of an element behave the same way chemically not because they have the same number of ___________, but because they have the same number of ____________.
Protons or neutrons electrons
__________isotopes are often used to label or "tag" specific molecules and then follow their progress either in a chemical reaction or in living cells and tissues.
Radioactive
isotopes, such as carbon-14, are unstable and tend to break apart into elements with lower atomic numbers while releasing a significant amount of energy.
Radioactive
When a larger atom breaks apart into smaller atoms, along with the release of a significant amount of energy, this is referred to as which of the following?
Radioactive decay
Chemical reactions that involve a transfer of electrons from one atom to another are called
Redox reactions
Hydrophobic substances tend to do which of the following?
Repel water Aggregate together when mixed with water in order to minimize contact with water Assume shapes that minimize contact with water
The property of _______ heat measures the extent to which a substance resists changing its ____________ when it absorbs or loses heat.
Specific Temperature
What shape do s orbitals assume?
Spherical
What is the main downside to using radioactive isotopes to label molecules within living cells?
Subatomic particles emitted by unstable isotopes may damage living cells.
Because of the many hydrogen bonds that form between its molecules, water has a very high ___________. This allows small insects to "walk on water."
Surface tension
When the pH of a solution rises by 1 which of the following happens?
The [H+] decreases 10-fold
Which of the following is the definition of the heat of vaporization of water?
The amount of energy needed to change 1 g of water from a liquid to a gas
Atoms are chemically the most stable when which of the following occurs?
Their outer shell is full.
Why does water rise inside a glass tube with a narrow diameter (a capillary)?
There are electrical charges on the surface of the glass.
Why is an atom electrically neutral?
There are equal numbers of protons and electrons in the atom.
Which of the following describes hydrogen bonds? They are about 5 - 10% as strong as covalent bonds. They are stronger than covalent bonds. They are stronger than ionic bonds. They are about 90% as strong as covalent bonds.
They are about 5 - 10% as strong as covalent bonds
Water is cohesive. Which describes this feature of water molecules? They are attracted to ions. They are attracted to other (not water) polar molecules. Reason: Read the question carefully - it asks you to define the word "cohesive." Cohesive refers specifically to the fact that water molecules tend to be attracted to other molecules. The tendency of water molecules to be attracted to other (not water) polar molecules is called adhesion. They are held together by strong covalent bonds. They are attracted to each other.
They are attracted to each other.
Which of the following statements about polar molecules are true?
They are electrically neutral. They have the same number of protons and electrons.
Choose all statements that describe atoms that have unfilled electron shells?
They can form bonds with other atoms They are chemically reactive. They can form chemical compounds.
Which of the following are some possible harmful effects of radioactive isotopes in cells?
They can lead to cell death in high doses. They can produce genetic mutations.
The different energy levels of electrons within atoms can be described as which of the following?
They can only take certain discrete values that correspond to quanta.
Why do elements in the same chemical group have the same bonding properties?
They have the same number of valence electrons
Carbon and silicon are both found in the same group of the periodic table. Carbon shares very similar bonding properties with silicon due to which of the following?
They have the same number of valence electrons.
Consider two electrons. One is located in the 2s orbital of an atom and the other in a 2p orbital of the same atom. Which of the following statements about those two electrons is true?
They have the same potential energy.
Hydrogen bonds are important for which reasons? They help maintain the structure of DNA and proteins. They play a key role in determining the properties of water. They hold the atoms of a single water molecule together. Reason: A single water molecule is held together by two polar covalent bonds; hydrogen bonds form between different water molecules. They are almost as strong as covalent bonds.
They help maintain the structure of DNA and proteins. They play a key role in determining the properties of water.
If two atoms belong to the same element, which of the following must be true?
They must have the same number of protons.
Elements, such as zinc and iodine, which are found in very small amounts in living things, but play crucial roles in biological processes, are known as which of the following?
Trace elements
Many animals have adapted to cool themselves by sweating. Which property of water allows for this adaptation?
Water's high heat of vaporization
The evaporation of water from body surfaces can significantly cool an organism. This is due to what property of water?
Water's high heat of vaporization
Water helps living things maintain a relatively constant internal temperature and protects cells from overheating due to the heat released by chemical reactions. What property of water is responsible for that?
Water's high specific heat
Buffers stabilize pH by releasing hydrogen ions when a(n) ____________ is added and absorbing hydrogen ions when a(n) _____________ is added.
base acid
Acidosis refers to a(n) ______ in the pH of human blood, and alkalosis refers to a(n) ______ in the pH of human blood.
decrease; increase
Carbon-12, carbon-13, and carbon-14 are
different isotopes of the same element
If an atom gains or loses a(n) ----------, it acquires a net electrical charge and becomes an ion.
electron
A nonpolar covalent bond involves an equal sharing of one or more pairs of
electrons
A base is a substance that lowers [H+] and decreases the pH when it dissociates in water lowers [H+] and increases the pH when it dissociates in water raises [H+] and increases the pH when it dissociates in water Reason: Bases increase the pH, because they lower the H+ concentration in a solution. The lower the amount of H+ is in a solution, the higher its pH is. raises [H+] and decreases the pH when it dissociates in water
lowers [H+] and increases the pH when it dissociates in water
If two electrons occupy different orbitals, they
may or may not have the same potential energies.
One ____________of the element carbon contains 6.02 x 1023 atoms of carbon.
mole
Which of the following amounts of a substance has a weight in grams equal to the combined atomic masses of all atoms that make up one molecule of the substance?
mole
one ____________ of a substance has a weight in grams equal to the combined atomic masses of all atoms that make up one molecule of the substance.
mole
One_______ of sucrose contains 6.02 x 1023 ____________of sucrose.
mole molecules
