In the extraction of iron, limestone is added as a flux to remove:
A. Copper sulfide
B. Silica (sand)
C. Alumina
D. Iron oxide
Answer: Option B
Solution (By JKSSB Mock Tests)
In a blast furnace, limestone (CaCO₃) decomposes to CaO, which acts as a basic flux. It reacts with the acidic impurity silica (SiO₂) to form calcium silicate slag (CaSiO₃), which is lighter and floats on top of the molten iron, allowing it to be separated and removed.
Explanation:
Soap molecules have a hydrophilic ionic head (COO⁻Na⁺) and a long hydrophobic hydrocarbon tail. In water, the tails aggregate away from water, forming a spherical micelle with heads outward. The hydrophobic core dissolves oily dirt, which is then washed away. This structure is stabilized by ion-dipole interactions. Detergents work similarly but with different head groups.
Explanation:
Lead-acid batteries use dilute H₂SO₄ as electrolyte. The electrodes are Pb and PbO₂. During discharge, both plates form PbSO₄ and the acid concentration decreases. Recharging reverses the reaction.
Explanation:
Dilute HNO₃ is an oxidizing agent; it oxidizes the hydrogen produced to water and itself gets reduced to nitrogen oxides (NO, N₂O, etc.). Very dilute HNO₃ with Mg/Mn can produce H₂. Metals above hydrogen normally displace H₂ from non-oxidizing acids like HCl.
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