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