निम्नलिखित कथनों पर विचार कीजिए :
कथन-I : चट्टानों के अपक्षय के कारणों में से एक कारण वर्षा है ।
कथन-II : वर्षा जल में घोल के रूप में कार्बन डाइऑक्साइड विद्यमान होता है ।
कथन-III : वर्षा जल में वायुमंडलीय ऑक्सीजन विद्यमान होता है ।
उपर्युक्त कथनों के संबंध में, निम्नलिखित में से कौन-सा सही है ?
सही उत्तर (A) (a) Both Statement-II and Statement-III are correct and both of them explain Statement-I है।
व्याख्या:
Weathering is a term which describes the general process by which rocks are broken down at the Earth's surface into such things as sediments, clays, soils and substances that are dissolved in water. Weathering can be biological, chemical or physical. Rainfall and temperature can affect the rate in which rocks weather. Greater rainfall increases the rate of chemical weathering. Rocks in tropical regions exposed to abundant rainfall and hot temperatures weather much faster than similar rocks residing in cold, dry regions. Hence, statement I is correct. Carbon dioxide from the air is dissolved in rainwater, making it slightly acidic. Normal rain has a pH of about 5.6, it is slightly acidic because carbon dioxide (CO2) dissolves into it forming weak carbonic acid. Hence, statement II is correct. A reaction can occur when the rainwater comes into contact with minerals in the rock, causing weathering. Acid rain usually has a pH between 4.2 and 4.4. Oxygen is one of the most important elements collected from falling rainwater. This dissolved oxygen is not the same as the oxygen in the water molecule. Dissolved oxygen is present in all rainwater and surface supplies due to contact with the atmosphere. Hence, statement III is correct. Rainwater is typically devoid of all dissolved solids but contains dissolved gases (oxides of carbon, nitrogen and sulphur) which result in pH values of about 5.5 or lower. From the above, we can conclude that both statement II and statement III are correct and explain statement I.
In English (Question & Model Answer)
Consider the following statements:
Statement-I: Rainfall is one of the reasons for weathering of rocks.
Statement-II: Rain water contains carbon dioxide in solution.
Statement-III: Rain water contains atmospheric oxygen.
Which one of the following is correct in respect of the above statements?
The correct answer is (A) (a) Both Statement-II and Statement-III are correct and both of them explain Statement-I.
Explanation:
Weathering is a term which describes the general process by which rocks are broken down at the Earth's surface into such things as sediments, clays, soils and substances that are dissolved in water. Weathering can be biological, chemical or physical. Rainfall and temperature can affect the rate in which rocks weather. Greater rainfall increases the rate of chemical weathering. Rocks in tropical regions exposed to abundant rainfall and hot temperatures weather much faster than similar rocks residing in cold, dry regions. Hence, statement I is correct. Carbon dioxide from the air is dissolved in rainwater, making it slightly acidic. Normal rain has a pH of about 5.6, it is slightly acidic because carbon dioxide (CO2) dissolves into it forming weak carbonic acid. Hence, statement II is correct. A reaction can occur when the rainwater comes into contact with minerals in the rock, causing weathering. Acid rain usually has a pH between 4.2 and 4.4. Oxygen is one of the most important elements collected from falling rainwater. This dissolved oxygen is not the same as the oxygen in the water molecule. Dissolved oxygen is present in all rainwater and surface supplies due to contact with the atmosphere. Hence, statement III is correct. Rainwater is typically devoid of all dissolved solids but contains dissolved gases (oxides of carbon, nitrogen and sulphur) which result in pH values of about 5.5 or lower. From the above, we can conclude that both statement II and statement III are correct and explain statement I.