List - IMolecule | List - IIBond enthalpy (kJ mol-1) |
---|---|
(A) HCl | (I) 435.8 |
(B) N2 | (II) 498 |
(C) H2 | (III) 946.0 |
(D) O2 | (IV) 431.0 |
Bond enthalpy is the energy required to break one mole of a particular bond in a gaseous substance.
A. HCl: The H-Cl bond enthalpy is approximately 431 kJ mol$^{-1}$ (slightly lower than HBr and higher than HF due to periodic trends down the halogen group). Thus, A-IV.
B. N$_2$: The N≡N triple bond is very strong, with a bond enthalpy of approximately 946 kJ mol$^{-1}$. Thus, B-III.
C. H$_2$: The H-H single bond has a bond enthalpy of approximately 436 kJ mol$^{-1}$. Thus, C-I.
D. O$_2$: The O=O double bond has a bond enthalpy of approximately 498 kJ mol$^{-1}$. Thus, D-II.
Therefore, the correct matching is A-IV, B-III, C-I, D-II.
A bob of heavy mass \(m\) is suspended by a light string of length \(l\). The bob is given a horizontal velocity \(v_0\) as shown in figure. If the string gets slack at some point P making an angle \( \theta \) from the horizontal, the ratio of the speed \(v\) of the bob at point P to its initial speed \(v_0\) is :