Which of the following catalysts is used in the hydrogenation of alkenes?
A. Fe
B. Pt or Ni
C. V₂O₅
D. MnO₂
Answer: Option B
Solution (By JKExamLibrary)
Hydrogenation of alkenes (addition of H₂ across double bond) is catalyzed by finely divided metals like nickel, platinum, or palladium. These adsorb H₂ and the unsaturated compound, facilitating reaction. V₂O₅ is for oxidation (Contact), MnO₂ for H₂O₂ decomposition, Fe for Haber process. Nickel is the most common industrial catalyst for hydrogenation.
Explanation:
Nitric acid (HNO₃) was called aqua fortis (strong water) due to its ability to dissolve metals like silver (except gold). Oil of vitriol is H₂SO₄; muriatic acid is HCl.
Assertion (A): Covalent compounds generally have low melting points. Reason (R): The intermolecular forces in covalent compounds are weak compared to ionic compounds.
A.A is false but R is true.
B.Both A and R are true but R is NOT the correct explanation of A.
C.Both A and R are true and R is the correct explanation of A.
Explanation:
Covalent compounds consist of molecules held together by weak van der Waals forces, unlike the strong electrostatic forces in ionic lattices. Therefore, less heat energy is required to break these intermolecular forces, resulting in low melting and boiling points. Both statements are true and R correctly explains A.
Explanation:
The modern periodic law states that the physical and chemical properties of elements are periodic functions of their atomic numbers. This was proposed by Henry Moseley, correcting Mendeleev's periodic table which was based on atomic mass. Atomic number determines the electronic configuration and thus chemical properties.
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