ch. 3 bio
Nitrogen (N) normally forms three covalent bonds with a valence of 5. However, ammonium has four covalent bonds, each to a different hydrogen (H) atom (H has a valence of 1). What do you predict to be the charge on ammonium?
+1
Assume that acid rain has lowered the pH of a particular lake to pH 4.0. What is the hydroxyl ion concentration of this lake?
1 x 10^-10 mol of hydroxide ions per liter of lake water
what is the hydrogen ion (H+) concentration of a solution of pH 8?
10^-8 M
which of the following dissociates completely in solution and is considered to be a strong base (alkali)
NaOH
Why does ice float in liquid water?
Stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water.
magnesium has an atomic number of 12. What is the most stable charge?
a +2 charge
what results from the chemical reaction illustrated above? The reactants have no charge.
a cation with a net charge of +1 and an anion with net charge of -1
which of the following can be attributed to water's high specific heat?
a lake heats up more slowly than the air around it
which of the following effects can occur because of the high surface tension of water?
a raft spider can walk across the surface of a small pond
which of the following is true for this reaction? 3 H2 + N2 -> <- 2 NH3
ammonia is being formed and decomposed simultaneously
Which bond or interaction would be difficult to disrupt when compounds are put into water?
covalent bonds between carbon atoms
How would acidification of seawater affect marine organisms?
decrease dissolved carbonate concentrations and hinder growth of corals and shell-building animals
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 (HCO3-) and a hydrogen ion (H+). Thus, H2CO3 ↔ HCO3- + H+ If the pH of the blood drops, one would expect
decrease in concentration of H2CO3 and an increase in the concentration HCO3
a strong acid like HCL ______________
dissociates completely in an aqueous solution
Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH3)?
each hydrogen atom has a partial positive charge, the nitrogen atom has a partial negative charge
which of the following is a property of liquid water?
has a heat of vaporization that is higher than that for most other substances
Which type of bond must be broken for water to vaporize?
hydrogen bonds
water molecules are attracted to one another by _____________
hydrogen bonds
consider the following reaction at equilibrium CO2 + H2O -><- H2CO3. What would be the effect of adding additional H2CO3?
it would drive the equilibrium dynamics to the left
which of the following takes place as an ice cube cools a drink?
kinetic energy in the liquid water decreases
You need to write down information about a molecule, but need to indicate only the type and number of atoms it contains. Which representation would work best?
molecular formula
Hydrophobic substances such as vegetable oil are
nonpolar substances that repel water molecules
in a single molecule of water, 2 hydrogen atoms are bonded to a single oxygen atom by ____________
polar covalent bonds
based on your knowledge of the polarity of water molecules, the solute molecule depicted here is most likely __________
positively charged
Rank, from low to high, the pH of blood, stomach acid, and urine.
stomach acid, urine, blood
the partial negative charge in a molecule of water occurs because _________
the electrons shared between oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus
The cities of Portland, Oregon, and Minneapolis, Minnesota, are at about the same latitude, but Minneapolis has much hotter summers and much colder winters than Portland. Why?
the ocean near Portland moderates the temperature
which of the following best describes the relationship between the atoms described below?
they are isotopes
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