Identify the atoms or groups from the following that exhibit $-R$ effect and $+R$ effect when present on a benzene ring:
$-OR, -NHCOR, -CN, -X, -NO_2, -NH_2, -CHO$

Given below are two statements:
Statement $I$: In $O_2N-C_6H_4-CH^+-C_6H_4-OCH_3$, the carbocation is stabilised by $+R$ effect of $-OCH_3$ group.
Statement $II$: In $O_2N-C_6H_4-CH^--C_6H_4-OCH_3$, the carbanion is stabilised by $-R$ effect of $-NO_2$ group.
In the light of the above statements, choose the correct answer from the options given below:

Rank the following compounds in order of increasing acidity (weakest acid first).

The higher stabilities of $tert$-butyl cation over isopropyl cation and $trans-2-butene$ over propene,respectively,are due to orbital interactions involving

Identify the correct statements from the following :
a) Change in hybridisation affects the electronegativity of carbon
b) The $p$ orbitals in ethene are mutually parallel
c) The number of $\sigma$ bonds in propyne is $6$
d) Electromeric effect is a permanent effect

The correct order of stability for the following alkoxides is:
$(A)$ $CH_3CH(NO_2)O^-$
$(B)$ $CH_2=C(NO_2)O^-$
$(C)$ $O_2N-CH=CH-O^-$