What do you mean by ozone hole? What are its consequences?
In Polar Regions, stratospheric clouds provide the surface for chlorine nitrate and hypochlorous acid, which react further to give molecular chlorine. Molecular chlorine and HOCl are photolysed to give chlorine-free radicals.
Hence, a chain reaction is initiated. The chlorine-free radical is continuously regenerated, thereby depleting the ozone layer. This phenomenon is known as the 'Ozone hole'.
Effects of depletion of ozone layer
The ozone layer protects the Earth from the harmful UV radiations of the sun. With the depletion of the layer, more radiation will enter the Earth's atmosphere. UV radiations are harmful because they causes the ageing of skin, cataract, skin cancer, and sunburns. They cause death of many phytoplanktons, which leads to decrease of fish productivity. Excess exposure may even cause mutation in plants.
Increase in UV radiations, decreases the moisture content of the soil and damages both plants and fibres.
Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?
What are the harmful effects of photochemical smog and how can they be controlled?
Write down the reactions involved during the formation of photochemical smog.
What are the reactions involved for ozone layer depletion in the stratosphere?
Explain tropospheric pollution in 100 words.
What would have happened if the greenhouse gases were totally missing in the earth's atmosphere? Discuss.
Statues and monuments in India are affected by acid rain. How?
What do you mean by green chemistry? How will it help decrease environmental pollution?
What is smog? How is classical smog different from photochemical smog?
A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason for the fish kill.
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?
Explain the formation of a chemical bond.
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?
Describe two important uses of each of the following: (i) caustic soda (ii) sodium carbonate (iii) quicklime.
Explain why the following systems are not aromatic?
Explain the significance of sodium, potassium, magnesium and calcium inbiological fluids.
For the following compounds, write structural formulas and IUPAC names for all possible isomers having the number of double or triple bond as indicated :
(a) C4H8 (one double bond)
(b) C5H8 (one triple bond)
What is meant by hybridisation of atomic orbitals? Describe the shapes of sp, sp2, sp3 hybrid orbitals.
How much energy is required to ionise a H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom (energy required to remove the electron from n =1 orbit).
Explain the principle of paper chromatography.
Define octet rule. Write its significance and limitations.
The drain cleaner, Drainex contains small bits of aluminum which react with caustic soda to produce dihydrogen. What volume of dihydrogen at 20 °C and one bar will be released when 0.15g of aluminum reacts?
Which of the two: OO2NCH2CH2O- or CH3CH2O- is expected to be more stable and why?