Who developed the modern periodic table based on atomic numbers?
A. John Newlands
B. Dmitri Mendeleev
C. Henry Moseley
D. Lothar Meyer
Answer: Option C
Solution (By JKSSB Mock Tests)
Henry Moseley established that the properties of elements are periodic functions of their atomic numbers, not atomic masses. This refined Mendeleev's table and resolved anomalies like Ar-K. The modern periodic table is thus based on Moseley's work. Mendeleev proposed the original table based on atomic masses. Newlands gave Law of Octaves. Meyer plotted atomic volume curve.
Explanation:
A small amount of ethanol (alcohol) is added to chloroform to inhibit its oxidation by air to toxic phosgene (COCl₂) and HCl. Ethanol acts as a negative catalyst (stabilizer) by consuming any formed phosgene. MnO₂, Pt, Fe are positive catalysts. Negative catalysts are also called inhibitors, used to prevent undesirable reactions.
Explanation:
The 'lock-and-key' model explains enzyme specificity: the substrate fits into the active site like a key in a lock. Protein nature is general; specificity arises from 3D structure.
Explanation:
Manganese is extracted by the aluminothermic process (Goldschmidt thermite process) where Mn₃O₄ is reduced by aluminium: 3Mn₃O₄ + 8Al → 9Mn + 4Al₂O₃. This works for metals with less reactivity than Al but not too reactive. Sodium is extracted by electrolysis. Iron is extracted by smelting with coke. Zinc by carbon reduction/electrolysis.
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