Which type of isomerism is exhibited by acetic acid $(CH_3COOH)$ and methyl formate $(HCOOCH_3)$?

$n$-propyl alcohol and isopropyl alcohol are examples of

$HCN$ and $HNC$ are known as .............

Among the four compounds,$(i)$ acetone,$(ii)$ propanol,$(iii)$ methyl acetate and $(iv)$ propionic acid,the two that are isomeric are

How many isomers are possible for $C_{4}H_{10}O$?

Identify the pairs of compounds that represent chain isomerism among the following:
$I. CH_3-CH_2-CH_2-CH_2-OH$ (Butan$-1-$ol)
$II. CH_3-CH_2-CH(OH)-CH_3$ (Butan$-2-$ol)
$III. (CH_3)_3C-OH$ ($2$-Methylpropan$-2-$ol)
$IV. (CH_3)_2CH-CH_2-OH$ ($2$-Methylpropan$-1-$ol)