Although geometries of NH3 and H2O molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss.
The tetrahedral geometry shown by NH3 & H2O is
In NH3, the N atom is surrounded by three bond pairs (N—H) and one lone pair of electrons, which is present on the N atom. The repulsion shown by one lone pair in NH3 towards the three bond pair is very less because the number of bonding electrons is more as compared to lone pair of electron, as a result there will be less repulsion between the lone pair and bonding electrons. So, the bond angle is 107, nearer to normal tetrahedral bond angle of 109°.5’.
But in case of H2O, the O atom is surrounded by two bond pairs and two lone pair of electrons. Consequently, the repulsion will be stronger and greater between the lone pairs and bond pairs. The bond pairs will be repelled more by the lone pairs, resulting in decrease of bond angle to 104°, as compared to normal tetrahedral bond angle 109°.5’.
Therefore instead NH3 and H2O have tetrahedral geometry, still they have different bond angles.
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
Write Lewis symbols for the following atoms and ions:
S and S2–; Al and Al3+; H and H–
Draw the Lewis structures for the following molecules and ions: H2S, SiCl4, BeF2, , HCOOH
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.
Calculate the number of kJ of heat necessary to raise the temperature of 60.0 g of aluminium from 35°C to 55°C. Molar heat capacity of Al is 24 J mol–1 K–1.
What do you mean by ozone hole? What are its consequences?
What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?
Describe the structure of the common form of ice.
The pH of a sample of vinegar is 3.76. Calculate the concentration of hydrogen ion in it.
Do you observe any soil pollution in your neighbourhood? What efforts will you make for controlling the soil pollution?
Calculate the wavelength for the emission transition if it starts from the orbit having radius 1.3225 nm and ends at 211.6 pm. Name the series to which this transition belongs and the region of the spectrum.
An ion with mass number 37 possesses one unit of negative charge. If the ion contains 11.1% more neutrons than the electrons, find the symbol of the ion.
A 0.02 M solution of pyridinium hydrochloride has pH = 3.44. Calculate the ionization constant of pyridine
Anything that influences the valence electrons will affect the chemistry of the element. Which one of the following factors does not affect the valence shell?
(a) Valence principal quantum number (n)
(b) Nuclear charge (Z)
(c) Nuclear mass
(d) Number of core electrons.