- A${H_2}O\, \to \,{H_3}{O^ + }$
- ✓$B{F_3}\, \to \,BF_4^ - $
- C$C{H_4}\, \to \,{C_2}{H_6}$
- D$N{H_3}\, \to \,NH_4^ + $

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$F^-+ H_2O \rightleftharpoons HF + OH^-; K_b$
which relation is correct
$(A)$ $\mathrm{H}$ and $\mathrm{H}$
$(B)$ $\mathrm{H}$ and $\mathrm{C}_2 \mathrm{H}_5$
$(C)$ $\mathrm{C}_2 \mathrm{H}_5$ and $\mathrm{H}$
$(D)$ $\mathrm{CH}_3$ and $\mathrm{CH}_3$
Assertion $A$: In the photoelectric effect, the electrons are ejected from the metal surface as soon as the beam of light of frequency greater than threshold frequency strikes the surface.
Reason $R$ : When the photon of any energy strikes an electron in the atom, transfer of energy from the photon to the electron takes place.
In the light of the above statements, choose the most appropriate answer from the options given below :
$C{H_2} = CH - C \equiv C - C{H_2} - CN$
Statement $I :$ Bohr's theory accounts for the stability and line spectrum of $Li ^{+}$ ion.
Statement $II :$ Bohr's theory was unable to explain the splitting of spectral lines in the presence of a magnetic field.
In the light of the above statements, choose the most appropriate answer from the options given below:

