
- A

- B

- ✓

- D







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$(A)$ Kinetic energy of electron is $\propto \frac{ Z ^{2}}{ n ^{2}}$.
$(B)$ The product of velocity (v) of electron and principal quantum number (n), 'vn' $\propto Z ^{2}$.
$(C)$ Frequency of revolution of electron in an orbit is $\propto \frac{ Z ^{3}}{ n ^{3}}$.
$(D)$ Coulombic force of attraction on the electron is $\propto \frac{ Z ^{3}}{ n ^{4}}$.
Choose the most appropriate answer from the options given below :

$(i)$ $6C(s) + 3{H_2}(g) \to {C_6}{H_6}(l);\,\Delta H = + 45.9\,kJ$
$(ii)$ ${H_2}(g) + \frac{1}{2}{O_2}(g) \to {H_2}O(l);\,\Delta H = - 285.9\,kJ$
$(iii)$ $C(s) + {O_2}(g) \to C{O_2}(g);\,\Delta H = - 393.5\,kJ$
........$kJ$
