Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Ozone layer is formed of three oxygen atoms and known as the layer of protection which protects the earth from the UV rays. The photodissociation of ozone and generation are present in the equilibrium state. This ozone layer releases the energy of ultraviolet radiations as heat. So, ozone layer acts as the shield in the stratosphere which protect us from the harmful radiations. Decline in the thickness of the ozone layer over a restricted area is known as ozone hole. And, the chlorofluorocarbons are the main cause of the ozone depletion. CFCs are used as the coolants in refrigerators and air conditioners or as cleaning solvents etc. They get released into the troposphere and then they reach into the stratosphere and produce chlorine in the presence of the UV rays and these chlorine radicals does the ozone depletion by converting them into the oxygen.
This damage can be overcome by minimizing the release of chlorofluorocarbons. CFCs used as air conditioners or refrigerators should be replaced with environment friendly alternatives. Or CFCs released through the industries, should be controlled.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
Do basic solutions also have H+(aq) ions? If yes, then why are these basic?
Explain the mechanism of the cleaning action of soaps.
How are water and minerals transported in plants?
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
Why is respiration considered an exothermic reaction? Explain.
What determines the rate at which energy is delivered by a current?
What is the need for a system of control and coordination in an organism?
Why are we looking at alternate sources of energy?
When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
What would be the advantages of exploiting resources with short-term aims?