Chapter 2 MasteringBiology
Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?
10
Atoms with the same number of protons but with different electrical charges _____.
are different ions
Sodium chloride (NaCl) dissolves in water because water molecules _____.
are polar
Radioactive isotopes
can be used in conjunction with PET scans to diagnose diseases.
In some areas, fluoride is added during the municipal water treatment process in order to help
reduce tooth decay.
Grapefruit juice is approximately pH 3, and tomato juice is approximately pH 4. A glass of grapefruit juice contains _____ H+ as a glass of tomato juice.
ten times as much
In a group of water molecules, hydrogen bonds form between _____.
the oxygen atom in one molecule and a hydrogen atom in another molecule
The most widely effective solvent for organisms is a material that is _____.
polar
Pure water has a pH of 7, but some cases of acid precipitation have been recorded with a pH close to 3. This means that acid rain has a concentration of hydrogen ions that is _____ times the hydrogen ion concentration of pure water.
10,000
Chemical reactions do not create or destroy matter but simply rearrange it. Which example is the correct completed equation for this reaction? 4 NH3 + _____ O2 → _____ NO + _____ H2O
4 NH3 + 5 O2 → 4 NO + 6 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
What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
6
How are cohesion and surface tension related to the chemical properties of water?
All are properties related to hydrogen bonding.
Which of the following statements regarding matter is false?
All matter exists in the form of compounds.
Two atoms of the same element must have the same number of _____.
protons
The temperature of evaporation is much higher for water than for alcohol. Without knowing more about the chemistry of alcohol, which of the following is the most logical chemical explanation for this phenomenon?
Fewer hydrogen bonds form between alcohol molecules. As a result, less heat is needed for alcohol molecules to break away from solution and enter the air.
When water freezes, ice floats. Why?
In ice, the water molecules are farther apart than in liquid water.
Which of these refers to atoms with the same atomic number but different atomic masses?
These atoms are isotopes.
Which of the following statements is true about compounds?
They contain two or more elements in a fixed ratio to each other.
As of 2010, there are 118 known elements. Of those, how many are believed to be essential to human biology?
about 25
An ionic bond involves _____.
an attraction between ions of opposite charge
Which of the following bonds are arranged from strongest to weakest in a biological system?
covalent, ionic, hydrogen
An atom's reactivity is determined by its _____.
electron configuration
A solution contains only glycerol and fructose. There is ten times as much glycerol as fructose. Therefore, ...
glycerol is the solvent.
For most atoms, a stable configuration of electrons is attained when the atom __________.
has a completely filled outermost shell
The levels of carbon dioxide are expected to _____ of our oceans.
increase and lower the pH
In salt, what is the nature of the bond between sodium and chlorine?
ionic
Adding a base tends to _____ of a solution.
lower hydrogen ion concentration and increase the pH
A(n) _____ refers to two or more atoms held together by covalent bonds.
molecule
Which of the following subatomic particles has appreciable mass and lacks a charge?
neutron
A hydrogen atom has one electron. How many covalent bonds can hydrogen form?
one
Ionic bonds form when _____.
one atom transfers an electron to another atom
A 1 M solution contains
one mole of solute per liter of solution.
Phosphorus-32 (radioactive) has _____ than phosphorus-35 (normal).
three fewer neutrons
A solution is aqueous if ...
water is the solvent.
