CH.12 Env. Sci.

Which of these covalent bonds is most polar?

Al-Cl

If aluminum ions have a 3+ charge and a sulfur ions have a 2- charge, the compound aluminum sulfide is:

Al2S3.

The individual particles in a covalent crystal are

molecules.

The boiling temperature of water is so much higher than that of methane because water molecules are

polar.

Salt and gasoline are insoluble because

salt ions are too attracted to themselves to interact significantly with nonpolar gasoline molecules.

List the following bonds in order of increasing polarity:

N-N < N-O < N-F < H-F

In a molecular dipole, electrons are distributed You Answered

unevenly because the nuclear charge at one end of the molecule is stronger thus pulling electrons toward that side.

How many electrons are used to draw the electron-dot structure for acetylene (a covalent compound with the formula, C2H2)?

10

How many electrons are used to draw the electron-dot structure for hydrogen peroxide (a covalent compound with the formula H2O2)?

14

How many electrons are used to draw the electron-dot structure for calcium chloride (an ionic compound with the formula CaCl2)?

8

Mixtures can be separated into their components by taking advantage of differences in the chemical properties of the components. Why might this separation method be less convenient than taking advantage of differences in the physical properties of the components?

A chemical property involves a chemical change so that you no longer have what you had.

A molecule is

A group of covalently atoms bonded together

Atoms of nonmetallic elements form covalent bonds, but they can also form ionic bonds. How is this possible?

An ionic bond results when a nonmetallic elements gains an electron from a metallic element.

Plastic wrap is made of nonpolar molecules and is able to stick well to polar surfaces, such as glass, by way of dipole/induced dipole molecular attractions. How is it that plastic wrap also sticks to itself so well?

By way of induced dipole-induced dipole molec

Which of these covalent bonds is most polar?

F-As

If gallium ions have a 3+ charge and sulfur ions have a 2- charge, the compound gallium sulfide is:

Ga2S3.

Which of the following molecules is the most polar?

HCl

Why is a ruby gemstone considered to be a solution?

It is a homogeneous mixture of chromium in aluminum oxide.

Magnesium ions carry a 2+ charge and chloride ions carry a 1- charge. What is the chemical formula for the ionic compound magnesium chloride?

MgCl2

If magnesium ions have a 2+ charge and a oxygen ions have a 2- charge, the compound magnesium oxide is:

MgO.

If sodium ions, Na+, have a 1+ charge and sulfate ions, SO4-2, have a 2- charge, the compound sodium sulfate is:

Na2SO4.

Which bond is most polar?

O-H

Why doesn't the sodium atom gain seven electrons so that its third shell becomes the filled outermost shell?

Sodium's nuclear charge is not strong enough to hold that many more electrons.

Fish don't live very long in water that has just been boiled and brought back to room temperature. Suggest why.

The boiling process removes the air that was dissolved in the water. Upon cooling the water is void of its usual air content, hence, the fish drown.

What is the difference between a compound and a mixture?

The components of a mixture are not chemically bonded together.

Why can't the elements of a compound be separated from one another by physical means?

Their atoms are too tightly bound to one another.

Does an ionic bond have a dipole?

Yes, the ionic bond is an example of a very strong dipole.

The outer electrons of metal atoms differ from the outer electrons of nonmetal atoms in that the outer electrons of metals

all of the above

Water, H2O, and methane, CH4, have about the same mass and differ by only one type of atom. Why is the boiling point of water so much higher than that of methane?

all of the above

Both nitrogen and phosphorus are able to attract three more electrons to their outer shells because

all of the above.

A neutral hydrogen atom can attract an additional electron

because the additional electron finds room in the valence shell.

An atom loses an electron to another atom. Is this an example of a physical or chemical change?

chemical change involving the formation of positive ions

Classify the following bonds as ionic, covalent, or neither (O, atomic number 8; F, atomic number 9; Na, atomic number 11; Cl, atomic number 17; U, atomic number 92). O with F; Ca with Cl; Na with Na

covalent; ionic; neither

The most polar molecule shown above is

d

Oxygen has a low solubility in water because

dipole-induced dipole attractions are relatively weak

Atoms of a covalent bond are held together by the

electrical attraction two nuclei have for shared electrons.

What elements tend to form ionic compounds?

elements found on opposite sides of the periodic table

A hydrogen atom does not form more than one covalent bond because it

has only one electron to share.

Is the air in your house a homogeneous or heterogeneous mixture? You Answered

heterogeneous because of the dust particles it contains

When sugar is dissolved in water, the volume of water

increases because material is being added to it.

Covalent and ionic bonds differ in that

ionic bonds don't involve the sharing of electrons.

When a solution is concentrated

large amounts of solute are dissolved in solvent.

The atoms of materials that conduct electricity best tend to be held together by

metallic bonds.

The atoms of a polar covalent bond

must be of different elements

What type of chemical bond would you expect between two neon atoms (Ne, atomic number 10)?

none of the above

The neon atom tends NOT to gain any additional electrons because

of the repulsions they would experience with electrons in the same shell.

Sugar is not infinitely soluble in water because

of the strong molecular attractions that occur between sugar molecules.

The valence shells of two atoms that are covalently bonded

overlap

What type of chemical bond would you expect between a silicon atom (Si, atomic number 14) and an oxygen atom (O, atomic number 8)?

polar covalent

The greater the difference in electronegativity between two covalently bonded atoms,

the greater the polarity.

How many electrons are shared in a single covalent bond?

2

In the illustration shown above, pure material is found in box(es)

a, b, and c.

In terms of the periodic table, is there an abrupt or gradual change between ionic and covalent bonds?

There is a gradual change: the farther apart, the more ionic.

Would you expect to find more dissolved oxygen in polar or tropical ocean waters? Why?

There would be more dissolved oxygen in the polar oceans because the solubility of oxygen in water decreases with increasing temperature.

An individual carbon-oxygen bond is polar. Yet carbon dioxide, CO2, which has two carbon-oxygen bonds, is nonpolar because

Two of the above are reasonable.

A saturated solution of compound X in water has a greater concentration than does a saturated solution of compound Y. Does it follow that compound X is also more soluble in water?

Yes, compound X is more soluble than is compound Y because a greater concentration in water can be obtained.

What type of chemical bond would you expect between a calcium atom (Ca, atomic number 20) and a chlorine atom (Cl, atomic number 17)?

ionic

It is a homogeneous mixture of chromium in aluminum oxide.

its nuclear charge

The valence electrons of elements in the same atomic period are similar because elements in the same atomic period have the same number of

none of the above.

What type of chemical bond would you expect between two chlorine atoms (Cl, atomic number 17)?

nonpolar covalent