Effect of temperature on benzenediazonium during diazotization What will benezendiazonium ion become if it is not maintained at a temperature below $5\ °\mathrm{C}$ during diazotization?
Diazonium salts are prone to ejection of molecular nitrogen. The process is fairly slow for aromatic diazonium salts, so the salts are usually relatively stable around 0 celsius (alkyldiazonium salsts, though, are a completely different matter). In case of benzenediazonium resulting phenyl-cation is extremely active and will react with first nucleophile present, in many cases it is water, so the product would be phenol.