Chlorofluorocarbons MCQ

Answer: c. Stratosphere

Explanation: The second layer of the atmosphere, the stratosphere is located below the mesosphere and above the troposphere. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 15 to 35 kilometres (9 to 22 mi) above Earth, although its thickness varies seasonally and geographically. This layer absorbs most of the sun’s ultraviolet radiation ( around 97 to 99 %), which otherwise would potentially damage exposed life forms near the surface. 

Layers of the atmosphere are shown below:

Answer: d. Chlorofluorocarbons

Explanation: Increased UV radiation led to the depletion of the ozone layer that has threatened life on earth, with increased occurrence of skin cancer in humans as well as other ecological problems, to bans on the chemicals, and the latest evidence is that ozone depletion has slowed or stopped.

Answer: b. Late 1970

Explanation: The scientific journal Nature of 1985 stated that three scientists from the British Antarctic discovered abnormally low levels of ozone ( 4% reduction in the total amount of ozone ) over the South pole. This thinning of the ozone layer especially in the antarctic region is known as the ozone hole. The ozone layer exists in the stratosphere, a layer 10-50 km above the surface of the earth. Chlorofluorocarbons are those materials which are a main cause of depletion of the ozone layer. There are various other ozone-depleting substances (ODS) along with CFCs which are causing ozone depletion.

Answer: b. Stratosphere

Explanation: Stratosphere: The second layer extends 50 km above sea level and the famous ozone layer is present here that protects the earth from the UV radiations from the sun. As we know that this layer gives a smoother ride, this makes Jets fly comfortably in the lower stratosphere.

Answer: a. Ammonia

Explanation: Depletion of the ozone layer is due to the destruction of the stratospheric layer of the atmosphere by free radicals like chlorine and bromine. The chlorine molecules are broken down into chlorine atoms that combine with oxygen atoms of the ozone layer to form CIA molecules, with very little oxygen to form the ozone layer again. This leads to depletion of ozone molecules and thus in the ozone layer. Ammonia is a colourless gas and a compound of nitrogen and hydrogen with the formula NH3. It is a common nitrogenous waste, particularly among aquatic organisms. It is an important constituent of the pharmaceutical and medical fields.

Answer: d. Protect the ozone layer depletion

Explanation: The Montreal Protocol is an international treaty designed to protect the ozone layer. It acts by phasing out the production of numerous substances like chlorofluorocarbons ( CFCs ) that are responsible for the depletion of the ozone layer. Agreed on 16 September 1987, it entered into force on 1 January 1989. There are various ozone-depleting substances which are controlled by Montreal Protocol such as bromine and chlorine but there are some which are not controlled by Montreal Protocol such as Nitrous Oxide.

Answer: b. Chlorofluorocarbons are used as refrigerants

Explanation: Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), derivatives of methane, ethane, and propane. Commonly known by the name Freon. It is used as refrigerants, as aerosol applicants in medicinal applications, blowing agents, and degreasing solvents. The Montreal Protocol has replaced the use of chlorofluorocarbons with other products such as hydrofluorocarbons to protect against the further depletion of the ozone layer.

Answer: d. Poles

Explanation: Ozone layer is a layer which is protecting earth from sun’s UV radiations which are harmful to earth. In the months of September, October, and November, due to a special meteorological and chemical condition at the south pole, the size of the ozone hole can reach up to 20 -25 million square km. Tropic of Cancer is that northernmost latitude place where the sun can appear overhead directly. The Tropic of Capricorn is the southernmost latitude where the sun can appear overhead. The Equator is an imaginary line that divides the planet into the northern and southern hemispheres, located at 0-degree latitude.

Answer: c. The sun is closer to the planet during summer

Explanation: The sun is comparatively closer to the planet during summer causing the UV radiations to travel a shorter distance and reach us faster, thus resulting in the planet getting heated up. 

Answer: b. High tides

Explanation: The UV rays have a hazardous role in humans and cause cataracts ( clouding of the eyes ). Skin cancer can also be caused due to UV rays. It is advised to always protect the eyes and skin during summers. Plants and agricultural products are also affected by UVB radiation. These rays are also known to hurt the marine ecosystem and biogeochemical cycles.