Multiple Choice QuestionsThe orange solid on heating gives a colourless gas and a green solid which can be reduced to metal by aluminium powder. The orange and the green solids are, respectively
NH4Cr2O7 and Cr2O3
Na2Cr2O7 and Cr2O3
K2Cr2O7 and CrO3
(NH4)2CrO4 and CrO3
Match the following.
| List I | List II | ||
| (A) | Flespar | (I) | [Ag3SbS3] |
| (B) | Asbestos | (II) | Al2O3.H2O |
| (C) | Pyrargyrite | (III) | MgSO4.H2O |
| (D) | Diaspore | (IV) | KAlSi3O8 |
| (V) | CaMg3(SiO3)4 |
(A) (B) (C) (D)
IV V II I
(A) (B) (C) (D)
IV V I II
(A) (B) (C) (D)
IV I III II
(A) (B) (C) (D)
II V IV I
Diamond is hard because
all the four valence electrons are bonded to each carbon atoms by covalent bonds
it is a giant molecule
it is made up of carbon atoms
it cannot be burnt
A.
all the four valence electrons are bonded to each carbon atoms by covalent bonds
In diamond each carbon atom is linked to four other carbon atoms by sigma bond. Each C - C bond is formed by the overlapping of sp3 hybrid orbitals of each carbon atoms. Each carbon atom is present at the centre of a regular tetrahedron. Each carbon atom is surrounded by four other carbon atoms present at the corners of a regular tetrahedron. The octet of each carbon atom is complete. Structure of diamond is a rigid three dimensional network. This explain high density and hardness of diamond. Diamond is chemically inactive due to rigid three dimensional structure.
High energy is required to break the large number of C - C bonds present in diamond. This explain the high melting point of diamond.
Monosilane on coming in contact with air bums with a luminous flame producing vortex rings. These rings are of
SiO2
SiO
Si
H2SiO3
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