Arrange the following major elements present in the Earth's crust, in ascending order, in weight percentage : 1. Aluminium 2. Calcium 3. Silicon 4. Oxygen Select the answer using the code given below :
- A.3, 4, 1, 2
- B.4, 3, 1, 2
- C.2, 1, 3, 4
- D.1, 2, 3, 4
Correct answer
Explanation
The correct answer is C, 2, 1, 3, 4. By weight, calcium is the smallest of the four and oxygen the largest, so the ascending order is calcium, aluminium, silicon, oxygen. Oxygen makes up about 46.6 per cent of the Earth's crust by weight, silicon about 27.7 per cent, aluminium about 8.1 per cent and calcium about 3.6 per cent. Iron (about 5 per cent) comes between aluminium and calcium, and sodium, potassium and magnesium follow. Oxygen and silicon lead because most crustal rocks are silicate minerals such as feldspar and quartz, and aluminium is the most abundant metal in the crust. Option A is wrong because it puts silicon below oxygen at the start and ends with calcium, the lightest share. Option B is wrong because it is close to a descending order, starting with oxygen. Option D is wrong because it places aluminium below calcium. Exam tip: the crust's order by weight is O, Si, Al, Fe, Ca, Na, K, Mg, remembered as 'O Si Al Fe Ca'.
Practice Questions
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- A.Amarkantak plateau in Madhya Pradesh
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- B.Godavari
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