A very large volume of hydrogen can be accommodated by making
- (a)non-metallic hydrides.
- (b)hydrogen peroxide.
- (c)non-stoichiometric hydrides.
- (d)alkali metal hydrides.
Correct — C, non-stoichiometric hydrides. Many transition metals and their alloys (such as palladium) absorb hydrogen into the gaps of their metal lattice, forming interstitial or metallic hydrides whose composition is not a fixed whole-number ratio — hence 'non-stoichiometric'. These can soak up very large volumes of hydrogen gas relative to their own volume, which is why they are studied for safe hydrogen storage.
- (a)non-metallic hydrides. — Covalent (non-metallic) hydrides such as methane or ammonia are discrete, fixed-composition molecules and do not act as bulk hydrogen sponges.
- (b)hydrogen peroxide. — Hydrogen peroxide (H2O2) is a specific compound, not a means of storing large volumes of hydrogen gas.
- (d)alkali metal hydrides. — Alkali metal hydrides (for example NaH) are ionic, fixed-composition (stoichiometric) solids and do not take up the large, variable amounts of hydrogen that interstitial hydrides do.
Hydrides are grouped as ionic (saline), covalent (molecular) and metallic (interstitial). In metallic or interstitial hydrides, hydrogen atoms occupy gaps in a transition-metal lattice; their composition is variable, so they are called non-stoichiometric. Because they can hold a great deal of hydrogen, they are important for hydrogen storage.
The phrase 'very large volume of hydrogen' points to a material that absorbs hydrogen in bulk. Ionic and covalent hydrides have fixed formulae and store little, while interstitial (non-stoichiometric) hydrides can pack in far more.
- Interstitial (metallic) hydrides form when hydrogen occupies gaps in a transition-metal lattice.
- They are non-stoichiometric — their composition is not a fixed whole-number ratio.
- They can absorb large volumes of hydrogen, so they are explored for hydrogen storage.
- Hydrides are broadly ionic (saline), covalent (molecular) or metallic (interstitial).
Interstitial, non-stoichiometric hydrides absorb the most hydrogen — option (c).
- Choosing alkali metal hydrides — these are stoichiometric and store little hydrogen.
- Confusing hydrogen peroxide (a specific compound) with a hydrogen-storage material.
Asked by identifying which class of hydride stores large volumes of hydrogen (interstitial / non-stoichiometric).
No directly related past PYQ was found.
- practice — not a real PYQ
Interstitial hydrides are typically formed by
- (a)alkali metals
- (b)halogens
- (c)transition metals
- (d)noble gases
Answer(c) transition metals — hydrogen fits into the gaps of their lattice.
- practice — not a real PYQ
A hydride whose composition is not a fixed whole-number ratio is described as
- (a)ionic
- (b)stoichiometric
- (c)non-stoichiometric
- (d)covalent
Answer(c) non-stoichiometric — characteristic of interstitial metallic hydrides.