MCQ
Which transition in the hydrogen spectrum would have the same wavelength as the Balmer type transition from $n =4$ to $n =2$ of $He ^{+}$spectrum
- ✓$n =2$ to $n =1$
- B$n =1$ to $n =3$
- C$n =1$ to $n =2$
- D$n =3$ to $n =4$
$\frac{1}{\lambda( H )}= R (1)^2\left[\frac{1}{ n _1^2}-\frac{1}{ n _2^2}\right]$
$\frac{1}{\lambda\left( He ^{+}\right)}= R (2)^2\left[\frac{1}{2^2}-\frac{1}{4^2}\right]$
Given $\lambda( H )=\lambda\left( He ^{+}\right)$
$R (1)^2\left[\frac{1}{ n _1^2}-\frac{1}{ n _2^2}\right]= R (4)\left[\frac{1}{2^2}-\frac{1}{4^2}\right]$
$\frac{1}{ n _1^2}-\frac{1}{ n _2^2}=\frac{1}{1^2}-\frac{1}{2^2}$
On comparing $n _1=1$ and $n _2=2$
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$AB , A _2$ and $B _2$ are diatomic molecule. If the bond enthalpies of $A _2, B _2$ and $AB$ are in the ratio $1: 0.5: 1$, then the bond enthalpy of $A_2$ is $......\,kJ\,mol ^{-1}$ (Nearest integer)
$R - X \rightarrow R ^{\oplus} X ^{\ominus} \rightarrow R ^{\oplus} \| X ^{\ominus} \stackrel{ Y^\ominus }{\rightarrow} R - Y + X ^{\ominus}$
Ion pair Solvent separated ion pair
A student writes general characteristics based on the given mechanism as:
$(a)$ The reaction is favoured by weak nucleophiles
$(b)$ $R^ \oplus$ would be easily formed if the substituents are bulky
$(c)$ The reaction is accompained by recemization
$(d)$ The reaction is favoured by non-polar solvents.
Which observations are correct $?$