In the extraction of aluminium from bauxite, the reagent used to remove silica as an impurity is:
A. Cl₂
B. NaOH
C. HCl
D. CO
Answer: Option B
Solution (By JKExamLibrary)
Bauxite contains SiO₂ (silica) as impurity. In the Bayer's process, powdered bauxite is treated with hot concentrated NaOH solution. Alumina dissolves forming sodium aluminate (NaAlO₂), while silica does not dissolve and is filtered off. Alternatively, silica can be removed by adding lime during refining. The purified alumina is then electrolyzed in cryolite. NaOH selectively dissolves Al₂O₃ due to its amphoteric nature.
Assertion (A): Methanol is highly toxic and can cause blindness if ingested. Reason (R): Methanol is metabolized in the body to formaldehyde and formic acid.
A.Both A and R are true but R is NOT the correct explanation of A.
B.A is false but R is true.
C.A is true but R is false.
D.Both A and R are true and R is the correct explanation of A.
Explanation:
Methanol (wood alcohol) is highly toxic. When ingested, it is metabolized by the enzyme alcohol dehydrogenase into formaldehyde and then formic acid. Formic acid interferes with mitochondrial function, leading to metabolic acidosis, optic nerve damage, and blindness. Both statements are correct and R explains A.
Explanation:
The p-block includes elements from groups 13 to 18. Gallium (Group 13), Tin (Group 14), and Bismuth (Group 15) are all p-block elements. Zinc (Group 12) has a completely filled d-subshell (3d10) in its ground state and common oxidation states, placing it in the d-block.
Explanation:
Cement sets by hydration reactions forming C-S-H gel and Ca(OH)₂, even underwater. It's a chemical process, not drying. Gypsum controls the setting rate.
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