Question 1

Find the correct statement: A) Tritium is an isotope of hydrogen with three nucleons. B) Deuterium, ²H, forms weaker bonds than ¹H. C) Ortho- and para-hydrogen are isotopes of H₂ molecule.

Accepted Answer

Tritium is an isotope of hydrogen with one proton and two neutrons, totaling three nucleons.

Question 2

Which of the following reactions can be used for small-scale (laboratory) production of H₂:
(i) Copper and concentrated HCl.
(ii) Aluminium and warm concentrated NaOH solution.
(iii) Group 17 hydride and water.

A) (i) and (iii)
B) Only (i)
C) Only (ii)

Accepted Answer

The correct reaction for small-scale (laboratory) production of hydrogen sulfide (H2S) is (ii) Aluminium and warm concentrated NaOH solution. This reaction involves the use of aluminum metal with a strong base (NaOH) in the presence of water, which can produce hydrogen gas. However, for hydrogen sulfide specifically, a source of sulfur is needed, which is not provided in any of the given reactions. Therefore, none of the reactions directly produce hydrogen sulfide (H2S), but the closest option for producing hydrogen (a component of H2S) in a lab setting from the given choices is with aluminum and NaOH. The question seems to have a mistake in not providing a direct method for H2S production.

Question 3

Find the most common industrial process for the production of H₂: A) using electrolysis of water B) using fossil fuels and water C) using biological methods

Accepted Answer

The most common industrial process for the production of hydrogen (H₂) is through steam methane reforming, which involves using fossil fuels (primarily natural gas) and water.

Question 4

Why is catalyst frequently required for the reactions involving H₂ as a reactant? A) Hydrogen is a gas, it has low solubility. Catalyst can increase its solubility. B) Hydrogen is a small molecule that can easily escape any reaction. Catalyst prevents this by rapidly reacting with H₂. C) Due to the strong H-H bond, the reactions with H₂ have high activation energy. Catalyst is used to lower this activation energy.

Accepted Answer

The correct answer is C because hydrogen (H₂) has a strong H-H bond, resulting in high activation energy for reactions involving it. Catalysts are used to lower this activation energy, making the reactions more feasible.

Question 5

Under which conditions does hydrogen react via a radical mechanism?&#10;A) in a presence of a catalyst&#10;B) thermal or photochemical activation&#10;C) under high-pressure conditions.

Accepted Answer

Hydrogen reacts via a radical mechanism when there is thermal or photochemical activation, which provides the energy necessary to break the H-H bond and initiate radical reactions.

Question 6

Hydrogen forms ___________ with the majority of elements from groups 1 and 2.&#10;A) molecular hydrides&#10;B) metallic hydrides&#10;C) saline hydrides

Accepted Answer

Hydrogen forms saline hydrides with the majority of elements from groups 1 and 2. These are ionic compounds where hydrogen acts as a hydride ion (H-) donor, typically forming with more electropositive s-block elements.

Question 7

Classify the following molecular hydrides: (i) SiH₄ (ii) PH₃ and (iii) AsH₃. A) (i) is an electron-precise hydride, (ii) is an electron rich hydride, (iii) is an electron deficient hydride B) All three are electron rich hydrides C) (i) is an electron precise hydride, (ii) and (iii) are electron rich hydrides

Accepted Answer

SiH4 is an electron-precise hydride because it has the exact number of electrons to form stable bonds without any lone pairs or electron deficiencies. PH3 and AsH3 are electron-rich hydrides because they have lone pairs on the central atom (P or As), giving them more electrons than needed for bonding.

Question 8

The metallic hydrides frequently have ____________ and ____________.&#10;A) (constant composition) and (are hard materials)&#10;B) (non-stoichiometry) and (metallic lustre)&#10;C) (good solubility) and (low reactivity)

Accepted Answer

Metallic hydrides often exhibit non-stoichiometry, meaning their composition can vary within certain limits rather than being fixed. They also tend to have a metallic lustre, similar to the metals from which they are formed.

Question 9

Hydrogen bonding is important for:&#10;A) molecular hydrides&#10;B) metallic hydrides&#10;C) saline hydrides

Accepted Answer

Hydrogen bonding is significant in molecular hydrides, where hydrogen is bonded to highly electronegative elements like nitrogen, oxygen, or fluorine, allowing for the formation of hydrogen bonds between molecules. This is not characteristic of metallic or saline hydrides, where the bonding nature and structure differ significantly.

Question 10

Which of the following statements is not correct:&#10;A) Hydride ligand can bridge two metallic centres in a polynuclear complex&#10;B) Since hydride is considered an anionic ligand, d-block hydrides cannot behave as acids.&#10;C) Both hydride and dihydrogen can be ligands to the same metal atom.

Accepted Answer

Hydride ligands in d-block metal hydrides can exhibit acidic behavior, contrary to the statement in option B. This is because the hydride (H-) can be protonated under certain conditions, releasing a hydrogen molecule (H2) and thus behaving as an acid.

Deck 10: Hydrogen