Analyzing the lone pairs of electrons in the given molecules.
\(H_2O\): Oxygen has 2 lone pairs, and each hydrogen atom has 0 lone pairs. Total = 2 lone pairs.
\(N_2\): Nitrogen in \(N_2\) has no lone pairs in the molecular structure. Total = 0 lone pairs.
\(CO\): Carbon in CO has no lone pairs, but oxygen has 2 lone pairs. Total = 2 lone pairs.
\(XeF_4\): Xenon in \(XeF_4\) has 2 lone pairs, and each fluorine atom has 3 lone pairs. Total = 2 lone pairs.
\(NH\_3\): Nitrogen in \(NH_3\) has 1 lone pair, and each hydrogen atom has 0 lone pairs. Total = 1 lone pair.
\(NO\): Nitrogen in NO has 1 lone pair, and oxygen has 2 lone pairs. Total = 3 lone pairs.
\(CO_2\): Carbon in \(CO_2\) has no lone pairs, and oxygen has 2 lone pairs on each oxygen atom. Total = 4 lone pairs.
\(F_2\): Each fluorine atom in \(F_2\) has 3 lone pairs. Total = 3 lone pairs. From the analysis, the molecules that contain only 2 lone pairs are \(H_2O\), \(CO\), and \(XeF_4\).
Therefore, the correct answer is 4 molecules.
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)

Cobalt chloride when dissolved in water forms pink colored complex $X$ which has octahedral geometry. This solution on treating with cone $HCl$ forms deep blue complex, $\underline{Y}$ which has a $\underline{Z}$ geometry $X, Y$ and $Z$, respectively, are
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)
A black body is at a temperature of 2880 K. The energy of radiation emitted by this body with wavelength between 499 nm and 500 nm is U1, between 999 nm and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien's constant, b = 2.88×106 nm-K. Then,