Biology 181 Ch 2

A hydrogen ion, formed during the dissociation of water, has a charge of which of the following?

+1

Molecules that are more polar tend to have which of the following characteristics?

- A higher specific heat - A higher heat of vaporization

Which of the following occurs because solid water is less dense than liquid water (choose all that apply)?

- Aquatic organisms can survive in liquid water below the frozen surface of ponds and lakes. - Ice floats. - Bodies of water freeze from the top down.

Water tends to repel or exclude which of the following? - Hydrophilic molecules - Polar molecules - Nonpolar molecules - Hydrophobic molecules - Ions

- Nonpolar molecules - Hydrophobic molecules

Select the molecules that tend to be hydrophobic. - Oils - Nonpolar molecules - Hydrocarbon chains (chains composed entirely of carbon and hydrogen atoms) - Ions - Polar molecules

- Oils - Nonpolar molecules - Hydrocarbon chains (chains composed entirely of carbon and hydrogen atoms)

The property of ____________ heat measures the extent to which a substance resists changing its _______________when it absorbs or loses heat.

- Specific heat - Temperature

Hydrogen bonds are important for which reasons?

-They play a key role in determining the properties of water. -They help maintain the structure of DNA and 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 Formula: Molarity = moles of solute / Liters of solvent

If a solution has a pH of 3, then its hydrogen ion concentration is which of the following?

1 x 10-3 M

Ionic bonds involve which of the following? (choose all that apply)

1. A transfer of electrons from one atom to another 2. An attraction between atoms with opposite electrical charges

Hydrophobic substances tend to do which of the following?

1. Aggregate together when mixed with water in order to minimize contact with water 2. Assume shapes that minimize contact with water 3. Repel water

Buffers stabilize pH by releasing hydrogen ions when a(n) _________ is added and absorbing hydrogen ions when a(n) ______________ is added.

1. Base 2. Acid

What are the two components of the key buffering system in human blood?

1. Carbonic acid 2. Bicarbonate

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)?

1. Electron energy levels 2. Electron shells

Which of the following statements are true

1. Even small changes in pH can alter the shape of enzymes and other proteins. 2. It is important for cells to maintain a fairly constant pH. 3. Most enzymes in living systems are extremely sensitive to pH.

How does water's high specific heat affect living organisms?

1. It helps prevent organisms from overheating due to the thermal energy released by chemical reactions inside cells. 2. It helps organisms maintain a relatively stable internal temperature when the external temperature rises or falls.

Which of the following statements are true?

1. It is important for cells to maintain a fairly constant pH. 2. Even small changes in pH can alter the shape of enzymes and other proteins. 3. Most enzymes in living systems are extremely sensitive to pH.

How does water's high specific heat affect living organisms?

1. The temperature of dry air tends to fluctuate more than the temperature of humid air. 2. Organisms that live in water generally experience a more stable environmental temperature than organisms that live on land.

Which of the following statements about polar molecules are true?

1. They are electrically neutral. 2. They have the same number of protons and electrons.

Which of the following are some possible harmful effects of radioactive isotopes in cells?

1. They can lead to cell death in high doses. 2. They can produce genetic mutations.

How does water's high heat of vaporization affect living organisms?

1. When your body is wet, you feel cooler than when your body is dry. 2. Many organisms sweat or pant in order to cool themselves.

The angle between the two O-H covalent bonds in a molecule of water is how many degrees (to the tenth place)?

104.5

No orbital can contain more than _______ electrons.

2

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

No orbital can contain more than

2 electrons

A molar concentration of 2 M is equal to:

2 mol/ L

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

The pH inside most cells and of the fluid surrounding the cells of multicellular organisms is fairly close to which pH?

7

he neutral point of the pH scale is

7

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 bonds involves the sharing of one or more pairs of electrons?

A covalent bond

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 alkaline range of the pH scale?

Any pH value above 7

Which of the following best describes the entire acidic range of the pH scale?

Any pH value below 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 increases.

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.

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

Explain why the organic substance C2H5OH is considered a compound?

Because it contains molecules made of atoms of different elements

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

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.

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

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

Which of the following molecules are nonpolar?

CH4 O2 N2

What do we call the ability of water to rise inside a tube of narrow diameter against the pull of gravity?

Capillary action

The four most abundant elements in living organisms are

Carbon Hydrogen Nitrogen Oxygen

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.

Valence electrons and their interactions determine the __________ properties of an element.

Chemical

A chemical reaction involves the breaking and formation of ______ _______

Chemical Bonds

Chemical bonds are broken and new bonds are formed during a(n)

Chemical Reaction

For any given isotope, such as C-14, the rate of decay can be described as which of the following?

Constant

In structural formulas, each solid line between atomic symbols represents a single _______ bond.

Covalent

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

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 Ionic Hydrogen Hydrophobic Interaction Van der Waals attraction

Atomic mass is measured in which of the following units?

Daltons (Da)

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

Atoms differ in their affinity for ________ called electronegativity.

Electrons

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

It takes work to keep electrons in their orbitals due to which of the following?

Electrons are attracted to the nucleus.

A substance that cannot be broken down into simpler substances by ordinary chemical means is called a(n)

Element

In order for an electron to move to a more distal orbital which of the following must occur?

Energy must be added (endergonic reaction)

In living systems, which of the following catalyze almost every chemical reaction necessary for life?

Enzymes

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.

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

Order the following atoms in increasing order of their electronegativity, starting at the top with the least electronegative one.

H, C, N, O

Which of the following are molecular formulas?

H2 O2

Select the polar molecule.

H2O

Which of the following molecules is likely to have the highest specific heat and the highest heat of vaporization?

H2O

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

When an ion or a polar molecule, such as sucrose, dissolves in water, they are surrounded by multiple layers of water molecules, collectively called which of the following?

Hydration shell

________ atoms always have one proton.

Hydrogen

Identify the four most abundant elements in living organisms.

Hydrogen Oxygen Nitrogen Carbon

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

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

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

The tendency of nonpolar molecules to aggregate together in water is known as

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

Where are valence electrons found?

In the outermost energy level only

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

If an atom gains or loses electrons, it is known as which of the following?

Ion

The atoms in NaCl are held together by what type of bond?

Ionic

Atoms, in which the number of electrons does not equal the number of protons, are called

Ions

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

By determining the ratio of the different ___________ of carbon and other elements in a sample, scientists are able to accurately

Isotopes

Typically, as the temperature increases, what happens to the rate of a chemical reaction?

It also increases.

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.

Select the reasons that the molecule formed by two hydrogen atoms (H2) is stable

It has no net charge. It has no unpaired electrons. It is held together by a covalent bond.

Select the reasons that the molecule formed by two hydrogen atoms (H2) is stable.

It has no net charge. It is held together by a covalent bond. It has no unpaired electrons.

What does it mean when we say water is adhesive?

It is attracted to other polar molecules and ions.

As the concentration of reactants increases, so do the collisions between them, which causes which of the following?

It speeds up the chemical reaction.

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

When writing out structural formulas, covalent bonds are represented by solid ___________ between atomic symbols.

Lines

Arrange the following states of water in order from most dense to least dense (start with most dense at the top).

Liquid Solid Gas

During radioactive decay, an atom typically breaks up into elements with which of the following?

Lower atomic numbers

One Blank _____________ of the element carbon contains 6.02 x 1023 atoms of carbon.

Mole

One ___________ of the element carbon contains 6.02 x 1023 atoms of carbon. Please do not use abbreviations

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

Electrons that are farther from the nucleus always have which of the following?

More potential energy

Compared to covalent bonds, hydrogen bonds are which of the following?

Much weaker

Water carries two partial __________charges on the oxygen atom and two partial ______________________, one on each hydrogen atom.

Negative; Positive

Isotopes are atoms of the same element that differ in the number of which of the following?

Neutrons

Isotopes differ in the number of ________ they contain.

Neutrons

Can a catalyst change the equilibrium of a reaction?

No

A(n) _________ covalent bond involves an equal sharing of one or more pairs of electrons.

Non-Polar

What type of bond forms between 2 hydrogen atoms?

Nonpolar covalent

What type of bond forms between 2 identical atoms?

Nonpolar covalent

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

A single water molecule can spontaneously break apart (ionize) to form which of the following?

One positive hydrogen ion and one negative hydroxide ion

Electron __________ represent probability distributions for electrons, that is, regions surrounding the nucleus where there is the highest probability of finding electrons.

Orbitals

Which of the following atoms has the highest electronegativity?

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 and Hydrogen

If two atoms are joined by a polar covalent bond, the atom with the lower electronegativity will have a partial _________ charge.

Partial

A(n) _________covalent bond is formed by an unequal sharing of one or more electron pairs.

Polar

Which bond is formed by an unequal sharing of one or more electron pairs?

Polar covalent

If two atoms are joined by a polar covalent bond, the atom with the lower electronegativity will have a partial ____________ charge

Positive

How is the crystal structure of salt formed?

Positively charged sodium ions are attracted to negatively charged chloride ions.

Atomic number refers to the number of which of the following?

Protons

Within an atom, ______ and ______ have nearly equal masses, while ______ have a much smaller mass.

Protons; Neutrons; Electrons

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

_____________ 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 ________ reactions.

Redox

Chemical reactions that involve a transfer of electrons from one atom to another are called ________________reactions.

Redox

An atom participating in a chemical reaction gains one or more electrons. The process of gaining electrons in a reaction is called

Reduction

The amount of heat 1 g of a substance must absorb or lose to change its temperature by 1°C is called __________ ______________.

Specific Heat

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.

The property of ___________ _________ is a measure of how difficult it is to stretch or break the surface of a liquid.

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

Which of the following statements about nonpolar molecules are true?

The distribution of electrical charge is uniform They are electrically neutral

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 collide with each other more frequently.

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

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.

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.

Water is cohesive. Which describes this feature of water molecules?

They are attracted to each other.

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.

If two atoms belong to the same element, which of the following must be true?

They must have the same number of protons.

Which of the following (choose all that apply) correctly describe electrons within atoms?

They occupy discrete energy levels.

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

Arrange the following bonds in order from strongest to weakest. Start with the strongest at the top.

Triple Double Single Hydrogen

In a single covalent bond, _________ total electrons are shared (please enter the number of shared electrons).

Two

The molecule shown in these two diagrams is held together by which of the following bonds?

Two single polar covalent bonds

A(n) _________ molecule can break apart to form a positive hydrogen ion and a negative hydroxide ion.

Water

Which of the following are compounds?

Water Carbon dioxide Sodium chloride

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.

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.

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

The crystal of the ionic compound NaCl is composed of

a matrix of ions with a precise geometry.

A substance that increases [H+] and decreases pH when it dissociates in water is called a(n)

acid

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

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

A substance that decreases [H+] and increases pH when it dissociates in water is called a(n)

base

A(n) __________________ is a substance or a mixture of substances that act to resist changes in pH

buffer

Organic molecules are relatively complex molecules that contain a backbone of _________ atoms

carbon (C)

The key buffer in human blood is an acid-base pair consisting of _______________ acid and ____________________

carbonic bicarbonate

A(n) __________ is any substance that increases the rate of a reaction without being altered itself.

catalyst

A chemical reaction involves the breaking and formation of __________ _____________.

chemical bonds

The number and configuration of electrons determines an element's

chemical properties

Most multicellular organisms maintain the pH of the fluid surrounding cells at values that are

close to neutral

Because polar water molecules attract each other, water is said to be

cohesive

True, discrete molecules form when atoms are connected by

covalent bonds.

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

arbon-12, carbon-13, and carbon-14 are

different isotopes of the same element

What shape do p orbitals have?

dumbbell

A nonpolar covalent bond involves an equal sharing of one or more pairs of _____________

electrons

Atoms differ in their affinity for________, a property called electronegativity.

electrons

When electrons move closer to the nucleus ______________.

energy is released. (exergonic reaction)

The letters K, L, M, and so on are used to designate different

energy levels in an atom.

In living organisms, almost all chemical reactions are catalyzed by protein catalysts called

enzymes

In a double covalent bond, _________ total electrons are shared (please only enter the number of shared electrons).

four

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

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

The relatively weak, but numerous Blank 1Blank 1 hydrogen , Correct Unavailable 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

Substances that attract water are called ___________ ("water-loving") while substances that repel water are called__________("water-fearing").

hydrophilic hydrophobic

In living systems, ionic compounds generally exist as

individual ions.

Elements possessing all eight electrons (two for helium) in their outer energy level are said to be (choose all that may apply)

inert noble gases

Chemical bonds that form due to the attraction between oppositely charged atoms that have gained or lost electrons are called

ionic

Unlike ____________ bonds, which produce a crystal lattice, ____________ bonds are formed between 2 individual atoms, giving rise to true, discrete molecules.

ionic covalent

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.

Fish and other animals can survive at the bottom of a lake during winter because ice is _________ dense than liquid water.

less

Solid water ___________ dense than liquid water.

less

The stronger a base is, the ______ its concentration of hydrogen ions and the ______ its pH.

lower; higher

A base is a substance that

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 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 Blank ________ of sucrose.

mole molecules

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

Water tends to repel or exclude _____________ molecules.

nonpolar

Water tends to repel or exclude which of the following?

nonpolar hydrophobic

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

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

Among subatomic particles, each __________ has a charge of +1, each _________ has a charge of -1, and each ____________ has no charge.

proton electron neutron

The atomic mass of an atom is equal to the sum of the masses of its

protons and neutrons

Atoms of different chemical elements can be differentiated based on the number of

protons in the nucleus

Buffers stabilize the pH of solutions by ______ hydrogen ions when a base is added and ______ hydrogen ions when an acid is added.

releasing; absorbing

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 falls by 2,

the [H+] increases 100-fold.

The pH of a solution is defined as

the negative logarithm of the hydrogen ion concentration

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?

two