Why do aldehydes and ketones undergo nucleophilic addition reaction?

Why do aldehydes and ketones undergo nucleophillic addition recations ? Give two example each

ketones give nucleophilic addition reactions more readily.

Why alkynes undergo nucleophilic addition reaction while simple alkenes do not ?

Explain why aldehydes are more reactive than ketones towards nucleophilic addition reactions ?

What type of aldehyde and ketones undergo Cannizzaro's reaction ?

Why does benzene undergo electrophilic substitution reaction easily and nucleophilic substitution with difficulty ?

Explain S_N^2 reactions. What is the preference order of different alkyl halides to undergo nucleophilic substitution reaction via SN2 mechanism ?

Explain why alkyl halides undergo nucleopilic substitution reaction more easily as compared to aryl halides ?