At which concentration, phenol act as preservative

Why does 70% sugar syrup act as preservative ?

Among the following which one acts as a food preservative ? Aspartame, Aspirin, Sodium benzoate , Paracetamol .

The ionization constant of phenol is 1.0xx10^(-10) . What is the concentration of phenolate ion in 0.05 M solution of phenol? What will be its degree of ionization if the solution is also 0.01 M in sodium phenolate?