Write Lewis symbols for the following atoms and ions:
S and S2–; Al and Al3+; H and H–
(i) S and S2– Electronic configuration of S is [Ne]10 3s23p4, i.e it has 6 electrons in its valence shell,therefore The Lewis dot symbol of sulphur (S) is . The dinegative charge shows that there will be two electrons more in addition to the six valence electrons. The electronic configuration can be [Ne]10 3s23p6, Hence, the Lewis dot symbol of S2– is
.
(ii) Al and Al3+ The electronic configuration of Aluminium is [Ne]10 3s2 3p1, i.e the valence electron is 3,therefore The Lewis dot symbol of aluminium (Al) is . The tripositive charge on a species infers that it has donated its three electrons to other atom & its possible electronic configuration is [Ne]10 3s1. Hence, the Lewis dot symbol is
.
(iii) H and H– Hydrogen has electronic configuration of 1s1,it has 1 electron in its valence shell. The Lewis dot symbol of hydrogen (H) is . The uninegative charge infers that there will be one electron more in addition to the one valence electron. The possible configuration may be 1s2. Hence, the Lewis dot symbol is
.
What is meant by the term bond order? Calculate the bond order of: N2, O2,O2+,and O2-.
Use molecular orbital theory to explain why the Be2 molecule does not exist.
Explain the formation of H2 molecule on the basis of valence bond theory.
Compare the relative stability of the following species and indicate their magnetic properties:
O2,O2+,O2- (superoxide), O22-(peroxide)
Describe the hybridisation in case of PCl5. Why are the axial bonds longer as compared to equatorial bonds?
Which out of NH3 and NF3 has higher dipole moment and why?
Explain why BeH2 molecule has a zero dipole moment although the Be–H bonds are polar.
Discuss the shape of the following molecules using the VSEPR model:
BeCl2, BCl3, SiCl4, AsF5, H2S, PH3
Draw the Lewis structures for the following molecules and ions: H2S, SiCl4, BeF2, , HCOOH
Describe the change in hybridisation (if any) of the Al atom in the following reaction.
How do you account for the formation of ethane during chlorination of methane?
What are hybridisation states of each carbon atom in the following compounds ?
(i) CH2=C=O,
(ii) CH3CH=CH2,
(iii) (CH3)2CO,
(iv) CH2=CHCN,
(v) C6H6
What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30°C?
What are the common physical and chemical features of alkali metals?
Calculate the molecular mass of the following:
(i) H2O
(ii) CO2
(iii) CH4
Assign oxidation number to the underlined elements in each of the following species:
(a) NaH2PO4
(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
(e) CaO2
(f) NaBH4
(g) H2S2O7
(h) KAl(SO4)2.12 H2O
What is the basic theme of organisation in the periodic table?
Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only.
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure?
Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
The pH of milk, black coffee, tomato juice, lemon juice and egg white are 6.8, 5.0, 4.2, 2.2 and 7.8 respectively. Calculate corresponding hydrogen ion concentration in each.
Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only.
Round up the following upto three significant figures:
(i) 34.216
(ii) 10.4107
(iii) 0.04597
(iv) 2808
The value of Kc for the reaction
3O2 (g) ↔ 2O3 (g) is 2.0 ×10–50 at 25°C.
If the equilibrium concentration of O2 in air at 25°C is 1.6 ×10–2, what is the concentration of O3?
Write chemical reactions to show the amphoteric nature of water.
Which important property did Mendeleev use to classify the elements in his periodic table and did he stick to that?
Propanal and pentan-3-one are the ozonolysis products of an alkene? What is the structural formula of the alkene?
The type of hybridisation of boron in diborane is
(a) sp (b) sp2 (c) sp3 (d) dsp2
Which of the followings are Lewis acids? H2O, BF3, H+ and NH+4
Describe the usefulness of water in biosphere and biological systems.
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