In the coordination compound, K₄[Ni(CN)₄], the oxidation state of nickel is :

Bottles containing C₆H₅l and C₆H₅CH₂I lost their original labels. They were labelled A and B for testing A and B were separately taken in test tubes and boiled with NaOH solution. The end solution in each tube was made acidic with dilute HNO₃ and then some AgNO₃ solution was added. Substance B gave a yellow precipitate. Which one of the following statements is true for this experiment?

During dehydration of alcohols to alkenes by heating with conc. H₂SO₄ the initiation step is

Ethyl isocyanide on hydrolysis in acidic medium generates