Chemistry Test 4
F7
28/10/2011
Time allowed : 90 minutes
[Ar] 3d5 4s1
[Kr] 4d10
1.
(a)
1
1
2.
(1310329) x 103 = [ 6.63 x 1034 x 3.00 x 108 x 6.02 x 10 23 ]  
 = 1.22 x 107 m = 122 nm
1
1
3.
(a)
1x3
The Lewis structures are :
O2
O3
H2O2
(b)
4.
Descending order in OO bond length : H2O2
O3
O2
Bond order of OO bond in H2O2 is 1
Bond order of OO bond in O3 is 1.5, owing to the resonance effect
Bond order of OO bond in O2 is 2
The higher the bond order, the stronger the attraction between oxygen atoms, the shorter
bond length
(c) Descending order of solubility in water: H2O2
O3
O2
H2O2 forms various intermolecular hydrogen bonds with water molecules
Hydrogen bonds are stronger than van der Waals’ force
O3 is a polar molecule, it attracts with the polar water molecules
O2 is a non-polar molecule, the attraction between O 2 and H2O is the weakest
in descending order for the three species: O2, O3, and H2O2. Explain your arrangement.
1
½
½
½
½
(a)
1x4
½
(b)
shape of molecules
BF3
the central atom consists of three bond pair electrons.
1
½
½
½
½
BrF3
the central atom consists of three bond pair electrons and two lone pair electrons ½
NF3
the central atom consists of three bond pair electrons and one lone pair electrons ½
PF5
the central atom consists of five bond pair electrons.
BrF3 and NF3 are polar molecules.
½
½,½
5.
6.
Penta1,3diene and penta2,3diene are isomers.
(a) geometrical isomers of penta1,3diene
trans isomer
2
cis isomer
(b)
Structures of two enantiomers of penta2,3diene
2
(c)
Carbon-1 and carbon-5 : sp3 hybridisation
Carbon-2 and carbon-4 : sp2 hybridisation
Carbon-3 : sp hybridization
2
(a)
The Lewis structure of NO3 ion is
1
resonance occurs in NO3 ion, bond order of NO bond is 1.33
the attractions between N atom and O atom are equal, all bond lengths are equal
The electronegativity of F atom is higher than that of O atom
bond electron pairs are drawn to F atom,
bond pairbond pair repulsion becomes less significant. ½
The electronegativity of O atom is higher than that of H atom,
bond electron pairs are drawn to O atom,
bond pairbond pair repulsion becomes more significant.
½
½
½
½
(b)
½
½