Chapters 21 and 22 Homework

Question 1

How are the alkali metals generally isolated?

Answer 1

Reduction of the chloride salt by chemical or electrical means

Question 2

Which of the following is an amorphous silicate?

Answer 2

Glass

Question 3

Which of the following oxidation states is least likely?

Answer 3

F = +1

Question 4

Why is metal a good conductor of heat?

Answer 4

The electrons gain kinetic energy and pass it quickly to other electrons.

Question 5

Which of the following elements is the most resistive at room temperature?

Answer 5

Si

Question 6

Which of the following is true concerning insulators?

Answer 6

The valence band is completely filled

Question 7

Hydrogen fluoride is a liquid that boils at 20 °C. What accounts for this relatively high boiling point?

Answer 7

Strong hydrogen bonds

Question 8

What is required of an element to react with a noble gas?

Answer 8

It must be very electronegative

Question 9

All of the following are isotopes of hydrogen except:

Answer 9

unerium

Question 10

In space, there are large glowing clouds of gas. Because approximately 70% of the universe appears to be composed of hydrogen, these clouds probably are largely composed of hydrogen. These light emissions are due to excited electrons returning to their ground state. Hydrogen gas (H2 ) is very stable; how can these clouds glow?

Answer 10

It is not hydrogen gas we see glowing, but rather clouds containing hydrogen ions whose electrons are available for excitation.

Question 11

Diamond, graphite and buckminsterfullerene are all allotropes of carbon. How do they differ from each other?

Answer 11

These allotropes each have differing connectivities that make their structures distinct.

Question 12

Though cyanide ion is extremely toxic to living systems, it is commonly used in the extraction of gold. Why is this done?

Answer 12

The cyanide ion complexes with the gold to form a soluble complex, thus easily removing it from insoluble silicates

Question 13

Through what mechanism does carbon monoxide act as a poison?

Answer 13

It binds preferentially to hemoglobin . The cells become depleted of oxygen and death occurs.

Question 14

The energy gap between the valence band and the conduction band in silicon is 100 kJ/mol. The energy gap for germanium will be:

Answer 14

smaller

Question 15

Which of the following oxides would form an acidic solution in water?

Answer 15

CO2

Question 16

Some water softeners replace calcium and magnesium ions with sodium ions, why?

Answer 16

calcium and magnesium form insoluble salts with soap anions

Question 17

A catalyst must be used to facilitate the formation of ammonia from nitrogen gas and hydrogen gas. Why couldn’t the reaction be sped up simply by being heated?

Answer 17

The reaction is exothermic. Increasing the temperature actually decreases the rate of the reaction.

Question 18

Adenosine triphosphate (ATP) is referred to as the “energy currency” of the cell. What aspect of the molecule endows it with this characteristic?

Answer 18

The phospahte bonds are high energy. When the bond is cleaved, it provides usable energy to other chemical reactions in the cell.

Question 19

The predominant mineral component of human bone tissue is hydroxyapatite (Ca5(PO4 )3OH). Strontium-90, a radioactive isotope and a major component of nuclear fallout, is a serious health threat. These facts are related because:

Answer 19

Strontium-90 is able to replace the calcium atom in hydroxyapatite causing radiation damage in bones.

Question 20

Which of the following is an allotrope of phosphorus having acute bond angles, and an extreme volatility in air?

Answer 20

white phosphorus