22.1.2 Hydrogen

Question 1

Hydrogen

Answer 1

• Hydrogen gas can be produced by electrolysis of water, by reactions involving metals or through reforming reactions.
• Hydrogen has three isotopes.
• Binary hydrides are composed of hydrogen and one other element.
• Hydrogen gas has several commercial applications.

Question 2

note

Answer 2

• In its elemental state hydrogen is a colorless, odorless,
  tasteless diatomic gas. Hydrogen is the most abundant
  element in the universe, but is rare in its elemental state on earth because it escapes from the atmosphere.
• Hydrogen gas can be produced by electrolysis of water, by reactions involving metals, or through reforming reactions. Electrolysis is an attractive process because of the abundance of water, but it is very energy intensive. Reactions with metals such as iron are older methods for generating hydrogen gas no longer in use today.
• Today, hydrogen gas is produced through the reforming reaction. Additional production can be effected through the water gas shift reaction. It is also possible to produce hydrogen gas through the water gas reaction using coal as a source for carbon. The carbon monoxide (CO) produced can also be fed into the water gas shift reaction.
• Hydrogen has three isotopes. They are the only isotopes of an element that have their own names. The most abundant isotope, 1 H, has a nucleus that consists of a single proton. Deuterium, or 2 H, has one neutron and forms the hydrogen component of heavy water. It is often given the symbol “D”. Finally, tritium, or 3 H, is a radioactive isotope with a half-life of 12.3 y and is not found in nature.
• Deuterium and hydrogen exhibit isotopic differences that allow them to be separated. For example, the boiling points of heavy water and conventional water are slightly different allowing them to be separated by fractional distillation.

Question 3

note 2

Answer 3

• Binary hydrides are composed of hydrogen and one other element.
• Ionic hydrides consist of hydrogen and an alkali metal such a lithium, they are all basic and are strong reducing agents.
• Metallic hydrides consist of hydrogen and a transition metal. Metallic hydrides often retain their metallic characteristics because the hydrogen atoms are absorbed into the interstices of the metal atomic lattice.
• Finally, the molecular hydrides consist of hydrogen bonded covalently to another element.
• Hydrogen gas has several commercial applications.
• Hydrogen gas is often used with carbon monoxide to form methanol.
• All synthetic fertilizers are formed using the Haber-Bosch process that decomposes nitrogen gas (N 2 ) forming ammonia (NH 3 ), which can be further reacted to produce nitrate (–NO 3 ) compounds.
• Finally, hydrogen gas can be used to convert double bonds in unsaturated compounds like fats into saturated oils.

Question 4

Which best describes the conversion of the cis-double bonds of vegetable oil to trans-double bonds?

Answer 4

Isomerization

Question 5

Which process is not a commercial application that uses hydrogen as a reactant?

Answer 5

Conversion of fats to oils

Question 6

What is a distinctive feature of many interstitial hydrides?

Answer 6

The ratio of hydrogen atoms to metal atoms is variable, not fixed.

Question 7

Which is not a binary hydride?

Answer 7

OH −

Question 8

What is the product of the Haber-Bosch process?

Answer 8

NH3(g)

Question 9

Which reaction shows how hydrogen is formed from methane?

Answer 9

CH4 + H2O → CO + 3H2

Question 10

What is an isotope effect found in D2O and H2O?

Answer 10

The boiling point for D2O is 101 °C.

Question 11

Which reaction shows how hydrogen is formed in the water-gas shift reaction?

Answer 11

CO + H2O -> CO2 + H2

Question 12

All of the following are characteristics of hydrogen at room temperature except

Answer 12

Weightless

Question 13

Which atom has two neutrons and one proton?

Answer 13

Tritium