Campbell Mastering Biology Ch. 2
Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?
10 neutrons
What is the molecular mass of caffeine (C8H10N4O2)?
194.2
In molecules, Oxygen usually makes ____ bonds.
2
The innermost electron shell of an atom can hold up to how many electrons?
2
Balance the following equation: C8H18 + O2 → CO2 + H2O
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O
To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add ________ electron(s).
2 electrons
What is the mass number of an ion with 107 electrons, 159 neutrons, and a +1 charge?
267 (you're welcome)
In molecules, Nitrogen usually makes ____ bonds.
3
An atom's atomic number is 7. Its valence is most likely _____.
3 (Two electrons fill the first shell, and 5 go into the second (valence) shell. The atom needs 3 more electrons to fill the valence shell.)
In molecules, Carbon usually makes ____ bonds.
4
How many grams of glucose would you need to make 1 liter of an aqueous 0.5M glucose solution? (Atomic masses: C = 12.01, H = 1.008, O = 16.00.)
90.08 grams of glucose
What happens when two atoms form a chemical bond?
A chemical bond forms when two atoms transfer or share outer electrons to complete their outer shells
Which statement about relative potential energy of electrons is correct?
An electron in the 3 p orbital of the third electron shell has more potential energy than an electron in the 2 p orbital of the second electron shell.
What does the term electron orbital describe?
An electron orbital describes a three-dimensional space where an electron can be found 90% of the time.
True or false: melting ice is a chemical reaction.
FALSE. A chemical reaction alters the covalent bonding between atoms, making new kinds of molecules.
What is true of the relation between life and chemical equilibrium?
Living cells avoid chemical equilibrium by taking in energy and materials.
Is oxygen more or less electronegative than hydrogen?
MORE!
What is true of activation energy:
Molecules usually get it from thermal energy
Carbon-14 dating works for fossils up to about 75,000 years old. Most dinosaurs went extinct 65.5 million years ago. Can 14C be used to date dinosaur bones?
Nope! After 65.5 million years, too much of the 14C would have decayed to be able to measure it.
List nitrogen, hydrogen, carbon, and oxygen in terms of decreasing electronegativity (highest to lowest).
Oxygen --> Nitrogen --> Carbon --> Hydrogen
Which model most accurately represents the current view of the structure of the atom: probability model or planetary model?
Probability model
The researchers found that the Neanderthal fossil had approximately 7.80 × 10-3 as much 14C as was present in the atmosphere around the living Neanderthal and the plants it ate. Approximately how many half-lives have passed since the Neanderthal died?
SEVEN half-lives!
Radioactive uranium-235 has a half-life of 704 million years. If it was incorporated into dinosaur bones, could it be used to date the dinosaur fossils?
Yep! After 65.5 million years only about 1/10 of the 235U would have decayed, leaving plenty to measure in the fossils.
A carbon atom and a hydrogen atom form what type of bond in a molecule?
nonpolar covalent bond (atoms with similar electronegativities form nonpolar covalent bonds)
What does the prefix "non-" mean?
not (what a surprise)
What does the prefix "neutr-" mean?
of neither gender or type
An ionic bond is formed when...
one atom transfers an electron to another atom
Compared with 31P, the radioactive isotope 32P has...
one more neutron.
Which subatomic particle always has a positive charge?
proton
Changing the number of ______ would change an atom into an atom of a different element.
protons!
Compared to covalent bonds, ionic bonds:
rely much less on electron-sharing
A covalent bond is one in which electron pairs are:
shared! (sharing is caring)
What does the prefix "mono-" mean?
single (duh)
An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have....
10 neutrons
Under standard conditions the reversible reaction A + B → C + D has a ΔG∘ = -25 kJ/mol. What is ΔG when: T = 475 K, [A] = 0.5M, [B] = 0.2 M, [C] = 0.2 M, and [D] = 0.3 M?
-27 kJ/mol
An electrically neutral molecule has the formula C3H4O2N. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have with other atoms in the molecule?
1
In molecules, Hydrogen usually makes ____ bonds.
1
How many grams of water (H2O) are needed to react with 5.0 grams of ferric trichloride (FeCl3)? FeCl3 + 3 H2O → Fe(OH)3 + 3 HCl
1.7 g H2O
An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?
5
To calibrate the x-axis for Carbon 14 decay, you have to convert half-lives to number of years. Recall that 14C has a single half-life of 5,730 years. How many years make up 5 half-lives for 14C?
5,730 × 5 = 28,650 5,730 × number of half-lives = years in number of half-lives
What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
6 (This is an atom of carbon, an element with 6 protons. Atomic number is the number of protons in an atom.)
A positive ion with two units of charge has 10 neutrons and 8 protons. The ion also has:
6 electrons
The mass number of an atom is 15, and its atomic number is 7. The atom probably has ______ neutrons in the nucleus.
8
Two C atoms form a double bond. Each C is bound to two H atoms. What is true about this bond?
All the atoms lie in a plane.
What coefficients must be placed in the following blanks so that all atoms are accounted for in the products? C6H12O6 → _____ C2H6O + _____ CO2
C6H12O6 → 2 C2H6O + 2 CO2
Balance the following equation: C6H6 + H2 → C6H12
C6H6 + 3 H2 → C6H12
An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element _____ because _____________________.
Carbon; it has 6 protons
How do catalysts mainly speed reactions?
Catalysts always lower EA (activation energy), though they may have other effects as well. With a lower EA, a larger fraction of collisions can produce the transition state.
What fact is most important in explaining how molecules convert thermal energy to activation energy (EA)?
Distortion increases a molecule's potential energy.
True or false: the O-O bond is polar and the C-C bond is nonpolar.
FALSE! Both are nonpolar.
True or false: the first shell of an electron can have between 0 and 4 electrons.
FALSE! The first shell can only have 0, 1, or 2 electrons
Explain the following reaction: 4 Fe + 3 O2 → 2 Fe2O3
Four atoms of Fe react with 3 molecules of O2 to form 2 molecules of Fe2O3.
If you want a molecule that is highly polar, look for one that contains:
H-N (Nitrogen and Hydrogen differ in electronegativity more than any other bonded pair of atoms in the list, making the N-H bond most polar)
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
What name is given to the bond between water molecules?
HYDROGEN! Wooo!
What is true of the transition state?
It can break apart to yield either reactants or products, AND it is extremely unstable and lasts only an instant.
By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom's charge stay close to zero?
Shared electrons aren't always near oxygen.
True or false: Electrons determine the atom's size.
TRUE
True or false: Ions may form by transferring an atomic nucleus (with or without electrons) to another molecule.
TRUE
True or false: atoms tend to avoid having a partly filled valence shell.
TRUE
True or false: all reactions are reversible.
TRUE! (Some reactions look irreversible because the reverse reaction is very slow, but the laws of thermodynamics guarantee that all are reversible)
What is true of all atoms that are anions?
The atom has more electrons than protons.
What accounts for the high percentage of oxygen in the human body?
The human body is mostly made up of water (H2O), and there is one oxygen atom in each molecule of water.
What is true about the number of protons and electrons of an uncharged atom?
The number of protons is equal to the number of electrons.
Which of the following statements correctly describes any chemical reaction that has reached equilibrium?
The rates of the forward and reverse reactions are equal.
A chemist calculates that a certain reaction would result in ΔH = -9 kJ and T ΔS = +1 kJ. What can you conclude?
The reaction will occur spontaneously, because it decreases G.
What is true of the energy levels of electrons in shells?
The valence shell has higher energy than other occupied shells
Why do carbon atoms tend to make 4 covalent bonds?
The valence shell needs 8 electrons.
How do covalent bonds hold atoms together?
They fill shells without giving atoms much charge AND bring electrons closer to protons.
What bonds can form between atoms of equal electronegativity?
Van der Waals interactions can form between atoms of equal electronegativity
Which statement about weak bonds is correct?
Weak bonds are transient and easily reversible.
When do partial charges occur?
When a covalent bond links atoms of two kinds OR when atoms share electrons unequally
What does the prefix "anti-" mean?
against (obviously)
Radioactive decay is likely to occur when.....
an atom has too many neutrons.
What does an ionic bond involve?
an attraction between ions of opposite charge
A substance that cannot be broken down into other substances by ordinary chemical procedures is
an element!
In salt, what kind of bond is between sodium and chlorine?
an ionic bond!
Potential energy is always.....
associated with position or arrangement.
Atoms that have the same number of protons but different electrical charges are __________
different ions
The atoms of different phosphorus isotopes have _______
different numbers of neutrons
What does the prefix "de-" mean?
from/out of/ remove
A phrase that applies to covalent bonding and not other kinds of bonds is:
electron-sharing
In a double covalent bond, a carbon atom shares:
electrons in two orbitals (a double bond involves two orbitals, each with a shared pair of electrons)
What does the prefix "iso-" mean?
equal
What does the prefix "lip-" mean?
fat (think lipids)
What does the prefix "prim-" mean?
first
What does the prefix "proto-" mean?
first
What does the prefix "quad-" or "quat-" mean?
four (duh)
What refers to atoms with the same atomic number but different atomic masses?
isotopes
What does the suffix "-lysis" mean?
loosening/split apart
What is a trace element required by most living organisms?
magnesium
What does the prefix "poly-" mean?
many
When chemists and biologists want to show how atoms are bonded in a molecule, they usually use a.....
structural formula (this kind of model is designed to show which atoms are bound to one another, but it doesn't accurately picture the sizes of atoms.)
In the term trace element, the adjective "trace" means that...
the element is required in very small amounts
The reactivity of an atom arises from...
the existence of unpaired electrons in the valence shell.
Chemical equilibrium is reached when.....
the forward and reverse reactions occur at the same rate so that the concentrations of reactants and products remain the same
For the reaction ATP + H2O → ADP + Pi, the change in standard free energy (ΔG∘) is -30.5 kJ/mol. From this information we can conclude that.....
the forward reaction will be spontaneous under standard conditions. (note that ΔG∘ is less than zero)
What determines the types of chemical reactions that an atom participates in?
the number of electrons in the outermost electron shell
The type of bonding and the numbers of covalent bonds an atom can form with other atoms is determined by
the number of unpaired electrons in the valence shell
Two atoms always represent the same element if they have.....
the same number of protons.
What does the prefix "tri-" mean?
three (duh)
What does the prefix "ad-" mean?
to
What does the suffix "-phob" mean?
to fear
What does the suffix "-phil" mean?
to love <3
What does the prefix "co-" mean?
together/with
What does the prefix "di-" mean?
two (duh)
What is a molecule?
two or more atoms held together by covalent bonds (duh)
What does the prefix "hydro-" mean?
water (duhhh)
Hydrogen bonding is most often seen...
when hydrogen is covalently bonded to an electronegative atom
In the equation ΔG = ΔH - T ΔS, the change in the amount of disorder in the system is symbolized by
ΔS