Chemistry Class 10 Chapter 6 Important Questions

• Don't miss out on these free and reliable class 10 chemistry chapter 6 important questions with answers study materials for your exams.
• Important Multiple Choice Questions of Chapter Number 14: Atmosphere of Chemistry class 10th Urdu Medium.
• Important Short Questions of Chapter Number 14: Atmosphere of Chemistry class 10th Urdu Medium.
• Sources of Air Pollutants: As you know 99% of atmosphere consists of N2 and O2. Although, other gases are minor constituents, they can have major effects on our environment. Because atmosphere determines the environment in which we live. So, these minor constituents are safe upto a concentration limit. But in some areas this limit has been crossed considerably during the last 60 years because of human activities. Different sources of air pollutants are described as:
• (i) Oxides of Carbon (CO2 and CO)
• Sources of oxides of carbon are as follows:
• Both of these gases are emitted due to volcanic eruption and decomposition of organic matter naturally.
• However, the major source for the emission of these gases is the combustion of fossil fuels (coal, petroleum and natural gas). Fossil fuels burnt in combustion engine of any type of automobile, kiln of any industry or open air fires emit CO2 and CO. 
• Forest fires and burning of wood also emit CO2 and CO. Especially, when supply of oxygen is limited, emission of CO dominates.
• Greenhouse Effect and Global Warming: The CO2 forms a layer around the Earth like an envelope. It allows the heat rays of the Sun to pass through it and reach upto the Earth. These rays are reflected from the Earth surface and go back to upper atmosphere. Normal concentration of CO2 layer retains enough heat to keep the atmosphere warm. So, normal concentration of CO2 is necessary and beneficial for keeping the temperature warm. Otherwise, the Earth would have been uninhabitable. The Earth’s average temperature would be about -20°C, rather than presently average temperature 15°C. CO2 is not an air pollutant. Rather, it is an essential gas for plants as O2 is essential for animals. Plants consume CO2 in photosynthesis process and produce O2.
• Hence, increased concentration of CO2 layer absorbs the infrared radiations emitted by the Earth’s surface that prevents heat energy escaping from the atmosphere. It helps to stop surface from cooling down during night. As the concentration of CO2 in air increases, less heat energy is lost from the surface of the Earth. Therefore, the average temperature of the surface gradually increases. This is called greenhouse effect. This effect is proportional to amount of CO2 in air. Greater is amount of CO2, more is trapping of heat or warming. Due to increased warming this phenomenon is also called global warming.
• Effects of global warming: 1. Accumulation of carbon dioxide in air is resulting in increasing atmospheric temperature about 0.05 °C every year. 2. It is causing major changes in weather patterns. Extreme weather events are occurring more commonly and intensely than previously. 3. It melts glaciers and snow caps that are increasing flood risks and intense tropical cyclones. 4. Sea-level is rising due to which low lying areas are liable to be submerged, turning previously populated areas no longer habitable.
• Effects of acid rain: (i) Acid rain attacks the calcium carbonate present in the marble and limestone of buildings and monuments. Thus, these buildings are getting dull and eroded day by day. (ii) Acid rain increases the acidity of the soil. Many crops and plants cannot grow properly in such soil. It also increases the toxic metals in the soil that poison the vegetation. Even old trees are affected due to acidity of soil. Their growth is retarded. They get dry and die. (iii) Acid rain directly damages the leaves of trees and plants, thus limiting their growth. Depending upon the severity of the damage, plants growth can be hampered.