Chemistry - Study Mode

[#666] What is the element required for solar energy conversion ?
Correct Answer

(C) Silicon

Explanation

Solution: Photovoltaics (PV) use silicon solar cells to convert the energy of sunlight into electricity. Operates under the photoelectric effect which results in the emission of electrons.

[#667] Major portion of the earth’s crust is mainly constituted by
Correct Answer

(B) Oxygen and Silicon

Explanation

Solution: Oxygen is the most abundant element in the earth’s crust, comprising 46.6% or the crust by weight. Silicon 28%, aluminum 8.2%, iron 5.6%, calcium 4.2%, sodium 2.5%, magnesium 2.4%, potassium, 2.0%, and titanium 0.61% also comprise the crust. Given the abundance of oxygen and silicon, the silicates are the most abundant minerals in the earth’s crust.

[#668] In surgery, metal pins are used for joining together broken bones. These metal pins remain uncorroded in the body. What is the material of these pins?
Correct Answer

(D) Titanium

Explanation

Solution: Titanium metal is important for its strength, low density and corrosion resistance. It has bitter corrosion resistance and less reactivity than aluminium. Hence, Titanium pins remains uncorroded in the body.

[#669] Which one is the naturally occuring heaviest element?
Correct Answer

(C) Uranium

Explanation

Solution: The heaviest naturally stable element is uranium, but over the years physicists have used accelerators to synthesize larger, heavier elements.

[#670] Which of the following will replace hydrogen from acids to form salts ?
Correct Answer

(B) Na

Explanation

Solution: According to the reactivity series , elements which are above of hydrogen can replace hydrogen. Hence Sodium will replace hydrogen from acids to form salts.