Characteristics of Water
About _____ molecules in a glass of water are dissociated.
1 in 500,000,000
What is the charge on a hydronium ion?
1+
What is the charge on a hydroxide ion?
1-
Measurements show that the pH of a particular lake is 4.0. What is the hydroxide ion concentration of the lake?
10-10 M
Measurements show that the pH of a particular lake is 4.0. What is the hydrogen ion concentration of the lake?
10-4 M
What is the pH of an aqueous solution with the hydronium ion concentration [H3O+] = 2 x 10-14 M?
13.7
How many grams of the molecule in Figure 3.2 would be required to make 2.5 L of a 1 M solution of the molecule? (Carbon = 12, Oxygen = 16, Hydrogen = 1)
150
What is the mass number of an ion with 108 electrons, 159 neutrons, and a +1 charge?
268
How many grams of the molecule in Figure 3.2 would be required to make 1 L of a 0.5 M solution of the molecule? (Carbon = 12, Oxygen = 16, Hydrogen = 1)
30
How many electrons does nitrogen have in its valence shell?
5
What is the molar concentration of [H3O+] in a cola that has a pH of 3.120? (For help with significant figures, see Hint 3.)
7.59 × 10−4
A molecule of carbon dioxide (CO2) is formed when one atom of carbon (atomic number 6) is covalently bonded with two atoms of oxygen (atomic number 8). What is the total number of electrons that must be shared between the carbon atom and the oxygen atoms in order to complete the outer electron shell of all three atoms?
8
Which of these bonds is weakest?
A
How did this molecule form? A positively charged molecule. This molecule consists of three hydrogen atoms bonded to an oxygen atom.
A water molecule gained an hydrogen ion from another water molecule.
Which drawing depicts an atom that is inert or chemically unreactive?
E
Which of the following best describes chemical equilibrium?
Forward and reverse reactions continue with no effect on the concentrations of the reactants and products.
If an atom of sulfur (atomic number 16) were allowed to react with atoms of hydrogen (atomic number 1), which of the molecules below would be formed?
H-S-H
Which of these is the correct equation for the dissociation of water?
H2O + H2O <==> H3O+ + OH-
Which of the following ionizes completely in solution and is considered to be a strong acid?
HCl
Why isn't this insect drowning?
Surface Tension
How does the pH of the solution on the right compare with that of the solution on the left?
The solution on the right is basic relative to the solution on the left.
Which of the following statements is true about buffer solutions?
They maintain a relatively constant pH when either acids or bases are added to them.
A given solution contains 0.0001 moles of hydrogen ions [H+] per liter. Which of the following best describes this solution?
acidic: H+ donor
The tendency of an atom to pull electrons toward itself is referred to as its _____.
electronegativity
Each water molecule is joined to _____ other water molecules by ____ bonds.
four, hydrogen
Water molecules have a polarity, which allows them to be electrically attracted to other water molecules and other polar molecules by weak chemical bonds known as _____.
hydrogen bonds
In a neutral solution the concentration of _____.
hydrogen ions is equal to the concentration of hydroxide ions
What name is given to this molecule? A negatively charged molecule. This molecule consists of a hydrogen atom bonded to an oxygen atom.
hydroxide ion
What name is given to this molecule? A positively charged molecule. This molecule consists of three hydrogen atoms bonded to an oxygen atom.
hyrdonium ion
The molecule shown here is the simplest of organic compounds. It is called
methane
Compared with 31P, the radioactive isotope 32P has
one more neutron.
What is the pH of a solution with a hydrogen ion [H+] concentration of 10-8 M?
pH 8
The unequal sharing of electrons within a water molecule makes the water molecule _____.
polar
In this molecule, what type of bond is found between the oxygen and hydrogens?
polar covalent
An example of a hydrogen bond is the bond between
the H of one water molecule and the O of another water molecule.
One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO−3) and a hydrogen ion (H+). Thus, H2CO3↔HCO−3+H+ If the pH of the blood drops, one would expect
the HCO−3 to act as a base and remove excess H+ with the formation of H2CO3.
Many mammals control their body temperature by sweating. Which property of water is most directly responsible for the ability of sweat to lower body temperature?
the absorption of heat by the breaking of hydrogen bonds
Pure, freshly-distilled water has a pH of 7. This means that
the concentration of H+ ions in the water equals the concentration of OH- ions in the water.
Research indicates that acid precipitation can damage living organisms by
washing away certain mineral ions that help buffer soil solution and are essential nutrients for plant growth.
Which of the following is a hydrophobic material?
wax
