The incorrect statement among the following is:

Choose the incorrect statement among the following regarding noble gases:

For a reaction A$\to$B, enthalpy of reaction is $-4.2$ $\mathrm{kJ}\hspace{0.17em}{\mathrm{mol}}^{-1}$ and enthalpy of activation is $9.6$ $\mathrm{kJ}\hspace{0.17em}{\mathrm{mol}}^{-1}$. The correct potential energy profile for the reaction is:

1.		2.
3.		4.

A particular station of All India Radio, New Delhi, broadcasts on a frequency of 1,368 kHz (kilohertz). The wavelength of the electromagnetic radiation emitted by the transmitter is: [speed of light, $\mathrm{c}=3.0\times {10}^8$ ${\mathrm{ms}}^{-1}$]

In which one of the following arrangements the given sequence is not strictly according to the properties indicated against it?

Which of the following statements is correct for an irreversible isothermal expansion of an ideal gas?

1. $∆\mathrm{U}=0,<mspace\; width="1em"></mspace>∆{\mathrm{S}}_{\mathrm{total}}\ne 0$

2. $∆\mathrm{U}\ne 0,<mspace\; width="1em"></mspace>∆{\mathrm{S}}_{\mathrm{total}}=0$

3. $∆\mathrm{U}=0,<mspace\; width="1em"></mspace>∆{\mathrm{S}}_{\mathrm{total}}=0$

4. $∆\mathrm{U}\ne 0,<mspace\; width="1em"></mspace>∆{\mathrm{S}}_{\mathrm{total}}\ne 0$

Which pair of ions among the following list do not constitute an iso-electronic pair?

1. Mn²⁺, Fe³⁺

2. Fe²⁺, Mn²⁺

3. O^2–, F^–

4. Na⁺, Mg²⁺