Chemistry Exam Questions and Answers for Class 11 on “Hydrogen – Hydrides”.
1. Which of the following acts as a ligand in complex Hydrides?
a) H2
b) H–
c) H+
d) H
Answer: b
Clarification: In complex hydrides like Lithium aluminium hydride or lithium sodium hydride, the hydrogen acts as a ligand and it is attached to the central atom in complex hydrides, which are salt-like substances.
2. (BeH2)n is a ______________
a) covalent hydride
b) polymeric hydride
c) ionic hydride
d) metallic hydride
Answer: b
Clarification: Polymeric hydrides are formed by elements having electronegativity in the range of 1.4 to 2.0. Examples of polymeric hydrides are (BeH2)n, (AlH3)n etc. They are joined to each other through hydrogen bonding in order to form a larger unit.
3. The oxidation state of hydrogen in hydrides is -1.
a) true
b) false
Answer: a
Clarification: The compounds of hydrogen with metals and nonmetals are called hydrides and their Oxidation state is -1. The examples are sodium hydride, calcium hydride, magnesium hydride etc. There are many types of hydrides like ionic hydrides, molecular hydrides covalent hydrides etc.
4. Hydrides made from group 1 and 2 are known as ___________
a) complex hydrides
b) ionic hydrides
c) metallic hydrides
d) covalent hydrides
Answer: b
Clarification: Ionic hydrides are formed by elements of group 1 and 2 except beryllium and magnesium, by heating them in hydrogen. They are white colourless crystalline solid having a high melting point and boiling point and they are easily decomposed by water, carbon dioxide or Sulphur dioxide.
5. What is used for removing the last traces of water from organic compounds?
a) Hydrogen
b) Lithium aluminium hydride
c) Ionic hydrides
d) Molecular hydrides
Answer: c
Clarification: Ionic hydrides are very strong reducing agents. Alkali metal hydrides are used for making Lithium aluminium hydride, sodium Boron hydride etc and they are also used for removing last traces of water from organic compounds.
6. Molecular hydrides of formed from ______________
a) f-block elements
b) p- block elements
c) d-block elements
d) s- block elements
Answer: b
Clarification: Molecular hydrides are also called as covalent hydrides and they are formed by elements of p-block those having higher electronegativity than hydrogen. They are again divided into electron deficient hydrides, electron precise hydrides and electron rich hydrides.
7. Which of the following is an example Of electron rich hydride?
a) methanol
b) methane
c) aluminium hydride
d) ammonia
Answer: d
Clarification: Electron rich hydrides are the hydrides which have a greater number of electrons than required to form normal covalent bonds. Examples are the hydrides of group 15, 16 and 17, the excess electrons in these hydrides, are present as lone pairs of electrons.
8. Methane is a electron _________ hydride.
a) poor
b) deficient
c) rich
d) precise
Answer: d
Clarification: Electron precise hydrides are the hydrides which have an exact number of electrons, that are needed to form normal covalent bonds. Few examples are the hydrides of group 14 like methane, Silicon hydride etc.
9. Aluminium hydride is an electron deficient hydride.
a) true
b) false
Answer: a
Clarification: Aluminium hydride is a molecular hydride, because it does not have a required number of electrons to form the normal covalent bonds. So, aluminium hydride is also called as an electron-deficient hydride, therefore the above statement is true.
10. Interstitial hydrides are also called as ____________
a) complex hydrides
b) molecular hydrides
c) ionic hydrides
d) metallic hydrides
Answer: d
Clarification: Metallic hydrides are also known as interstitial hydrides, these are formed when the transition metals and the rare Earth metals combine with hydrogen. Molecular hydrides are nothing but covalent hydrides, where are ionic hydrides are formed from S block elements.
11. Metallic hydrides are powerful _____________ agents.
a) oxidizing
b) reducing
c) combining
d) separating
Answer: a
Clarification: The metallic hydrides are powerful reducing agents. They are formed from the combination of transition metals and rare Earth metals with hydrogen and they also exhibit metallic properties. They are non-stoichiometric hydrides.
12. LaH2.76 is an example of _______
a) molecular hydrides
b) metallic hydrides
c) covalent hydrides
d) ionic hydrides
Answer: b
Clarification: The metallic interstitial hydrides’ composition varies with temperature and pressure, they are non-stoichiometric in nature and example for this is LaH2.76. These hydrides are formed when transition metals and rare Earth metals combine with hydrogen.
13. The hydride gap is related to group ________
a) 7, 8
b) 7, 9
c) 7, 8, 9
d) 8, 9
Answer: c
Clarification: Metals of the group 7, 8 and 9 do not form hydrides under standard temperature and pressure and this region of the periodic table is called hydride gap. So the hydride gap is related to group 7, 8 and 9.
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