ALS4A - Section 4/ Bonding and Structure I (4.1 - 4.4 Ionic...

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Section 4/ Bonding and Structure I (4.1 - 4.4 Ionic bonding and Covalent bonding) / Suggested solutions/ SKH Bishop Baker Secondary School A-Level Chemistry Section 4 Bonding and Structure I (4.1 - 4.4 Ionic bonding and Covalent bonding) 80 IB Q.7 (d) (i) [1] (ii) Delocalization of electron occurs above or below N, O 1 and O 2 atoms, so N - O 1 and N - O 2 bonds have equal bond length and partial double bond character. N - O 2 bond is a single bond of longer bond length. [2] (iii) All bond lengths of N - O bonds are the same because of the delocalisation of electron over the whole nitrate ion. [1] 80 IIB Q.6 (e) (i) It is a puckered ring with bond angle of 107 o . [1] (ii) It is linear ion with bond angle of 180 o . [1] (f) (i) The shape is trigonal planar. [1] 1
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Section 4/ Bonding and Structure I (4.1 - 4.4 Ionic bonding and Covalent bonding) / Suggested solutions/ (ii) sp 2 . [1] (g) (i) The formula is AlCl 3 . N(C 2 H 5 ) 3 , which is a 1:1 adduct. [1] (ii) It is a dative bond. [1] 80 IIB Q.7 (a) (i) The electronic configurations of N and P are 1s 2 2s 2 2p 3 and [Ne] 3s 2 3p 3 respectively. Both N atom and P atom can form an octet with 3 chlorine atoms separately to give their trichlorides. There is no low energy level (lowlying) 2d orbital in N and the energy gap (difference) between 2s to 3s orbitals is so great that promotion of electron from 2s to 3s to form 5 unpair electrons is unfavoured , consequently, N cannot expand its octet. But, there are 3d orbitals in P such that excitation of electrons to 3d is possible and P can expand octet to form pentachloride. (ii) The lone pair electrons on the P is much more diffuse and thus the three bond pairs electrons are repelled more than those of N. As a result, the H - P - H angle in PH 3 is 93 o whilst the H - N - H in NH 3 is almost tetrahedral. (iii) As N is more electronegative than P, N-H bond is more polar than P-H bond, solvation occurs less readily in the case of PH 3 and hydrogen bonding even exists between NH 3 and H 2 O, PH 3 has a very low solubility in water. [7] 81 IA Q.4 (b) (i) and (ii) (i) Nature of Bond (ii) Physical State RbH I (s) CaF 2 I (s) AsH 3 C (g) GeCl 4 C (l) [2] (c) Al 3+ < Ba 2+ < VO 2 + < SO 4 2- (1 mark for each error in sequence) [1] (d) (i) (trigonal) bipyramidal. [ ½ ] (ii) sp 3 . [ ½ ] 81 IIB Q.6 (e) N has a lone pair of electrons which repels the 3N-F bonds away from a NF 3 plane hence 2
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Section 4/ Bonding and Structure I (4.1 - 4.4 Ionic bonding and Covalent bonding) / Suggested solutions/ trigonal pyramidal. [ ½ ] + [ ½ ] B does not have a lone pair electrons hence repulsion is not applicable . [ ½ ] + [ ½ ] 82 IA Q.2 (b) Ionic Covalent Molecular Metallic Units constituting the crystal lattice +ve and -ve ions atoms molecules +ve charged ions in a sea of electrons Binding force holding the constituent units electrostatic attraction attraction between +ve nuclei and shared electrons van der Waals’ forces attraction between +vely charged ions and electrons Example (one each) sodium chloride diamond iodine or naphthalene copper [ ½ each] (c) Water Deflection of jet towards rod .
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ALS4A - Section 4/ Bonding and Structure I (4.1 - 4.4 Ionic...

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