CBSE Class 11 Chemistry VBQs Environmental Chemistry

Question. Which of the following is not correct about carbon monoxide?
(a) It forms carboxyhaemoglobin.
(b) It reduces oxygen carrying ability of blood.
(c) The carboxyhaemoglobin (haemoglobin bound to CO) is less stable than oxyhaemoglobin.
(d) It is produced due to incomplete combustion.
Answer. C

Question. Among the following, the one that is not a greenhouse gas is
(a) sulphur dioxide
(b) nitrous oxide
(c) methane
(d) ozone.
Answer. A

Question. Which oxide of nitrogen is not a common pollutant introduced into the atmosphere both due to natural and human activity?
(a) N₂O₅
(b) NO₂
(c) N₂O
(d) NO 
Answer. A

Question. Which of the following is a sink for CO?
(a) Microorganisms present in the soil
(b) Oceans
(c) Plants
(d) Haemoglobin 
Answer. A

Question. Which one of the following is not a common component of photochemical smog?
(a) Ozone
(b) Acrolein
(c) Peroxyacetyl nitrate
(d) Chlorofluorocarbons 
Answer. D

Question. Which one of the following statements regarding photochemical smog is not correct?
(a) Carbon monoxide does not play any role in photochemical smog formation.
(b) Photochemical smog is an oxidising agent in character.
(c) Photochemical smog is formed through photochemical reaction involving solar energy.
(d) Photochemical smog does not cause irritation in eyes and throat. 
Answer. D

Question. Which one of the following is responsible for depletion of the ozone layer in the upper strata of the atmosphere?
(a) Polyhalogens
(b) Ferrocene
(c) Fullerenes
(d) Freons 
Answer. D

Question. About 20 km above the earth, there is an ozone layer. Which one of the following statements about ozone and ozone layer is true?
(a) It is beneficial to us as it stops U.V. radiation.
(b) Conversion of O₃ to O₂ is an endothermic reaction.
(c) Ozone is a triatomic linear molecule.
(d) It is harmful as it stops useful radiation. 
Answer. A

Question. Which one of the following statements is not true?
(a) Clean water would have a BOD value of 5 ppm.
(b) Fluoride deficiency in drinking water is harmful. Soluble fluoride is often used to bring its concentration upto 1 ppm.
(c) When the pH of rain water is higher than 6.5, it is called acid rain.
(d) Dissolved Oxygen (DO) in cold water can reach a concentration upto 10 ppm.
Answer. C

Question. Which one of the following statement is not true?
(a) pH of drinking water should be between5.5 – 9.5.
(b) Concentration of DO below 6 ppm is good for the growth of fish.
(c) Clean water would have a BOD value of less than 5 ppm.
Answer. B

Question. Green chemistry means such reactions which
(a) are related to the depletion of ozone layer
(b) study the reactions in plants
(c) produce colour during reactions
(d) reduce the use and production of hazardous chemicals.
Answer. D

Question. Environmental pollution is causing a serious threat on the earth. Due to combustion of fossil fuels, a number of  poisonous and harmful gases enter into the atmosphere. Every country has made strict laws for industries and individual citizens to keep pollution under control.

Now answer the following questions:

Question. Why is it advised not to sleep with burning coke angithi in a closed room on winter nights?
Answer: On burning coke, a lot of carbon monoxide is produced which causes anoxia.

Question. How does the combustion of motor fuels cause pollution of the atmosphere?
Answer: On burning motor-fuels, toxic oxides of nitrogen is formed which affect respiratory system.

Question. Name one natural source and one human activity by which SO₂ enters into atmosphere?
Answer: Due to volcanic eruption and through combustion of sulphur containing fuels.

Question. An ozone-layer is present at a height of 25-30 km from earth-surface which protects us from U.V. radiation. A hole in the ozone-layer is created due to human activity.

Now answer the following questions:

Question. Which activity has been causing ozone-hole?
Answer: Use of CFC’s

Question. What is the most serious effect of ozone-hole?
Answer: The most serious effect is that U.V. radiation reaches the earth-surface causing skin cancer.

Question. What has been done to protect ozone layer?
Answer: Use of CFC’s has been banned.

Question.  How does excess CO₂ gas pollute the atmosphere?
Answer: Excess CO₂ creates ‘greenhouse effect’ which increases the earth’s temperature.