The para-nitrotoluene is formed predominantly due to steric hindrance at the ortho position.

The predominant product is nitrotoluene, specifically ortho- and para-nitrotoluene due to the activating effect of the methyl group.

Aniline will undergo substitution the fastest due to the strong activating effect of the amino group, which donates electron density to the ring.

The product is benzene sulfonic acid, formed by the electrophilic substitution of sulfur trioxide on benzene.

The expected product is 2,4,6-tribromophenol, as phenol is highly reactive towards electrophilic substitution due to the hydroxyl group.

The product is benzene sulfonic acid, formed by the addition of a sulfonyl group to the benzene ring.

Toluene is a stronger electrophile due to the electron-donating effect of the methyl group.

Toluene is the most reactive due to the electron-donating effect of the methyl group, which activates the ring towards electrophilic substitution.

Nitrobenzene will not undergo electrophilic substitution readily because the nitro group is a strong deactivator and meta-director.

Ethylbenzene will undergo electrophilic substitution the fastest due to the electron-donating effect of the ethyl group.

The new substituent will most likely attach at the ortho position due to the activating effect of the electron-donating group.

The nitro group is a deactivating and meta-directing group, so the substitution occurs predominantly at the meta position.