What is a conjugated system? Give examples and explain its effect.

The decreasing order of acidic strengths of the following compounds is:

Identify the type of electromeric effect ($E$-effect) in the following reactions:
$(a) >C=C< + CN^{-} \to -C(CN)-C^{-}-$
$(b) >C=C< + H^{+} \to -C^{+}-CH-$

In which type of molecule are the electrons of a $\pi$ bond delocalized?

Arrange the following according to the instructions:
$(i)$ Arrange in descending order of acidic strength:
$CH_3COOH, (CH_3)_3CCOOH, (CH_3)_2CHCOOH, CH_3CH_2COOH$
(ii) Arrange in descending order of stability:
$\stackrel{+}{CH}_3, (CH_3)_3\stackrel{+}{C}, CH_3CH_2^+, (CH_3)_2\stackrel{+}{CH}$
(iii) Arrange in increasing order of acidic strength:
$CCl_3COOH, CH_3COOH, CHCl_2COOH, CH_2ClCOOH$
(iv) Arrange in increasing order of stability:
$(a)$ $CH_3CH=CH-CHO$
$(b)$ $CH_3\stackrel{+}{CH}-CH=C-O:^-$
$(c)$ $\stackrel{+}{CH}_2-CH=CH-C=O$
$(v)$ Arrange in decreasing order of stability:
$(I)$ $CH_2=CH-CHO$
$(II)$ $\stackrel{+}{CH}_2-CH=C-H$ (with $O^-$)
$(III)$ $:CH_2-CH=C-H$ (with $O^-$)

Arrange the following carbanions in decreasing order of stability $:$