Black-and-white photography is a commercial process that involves a phenol. Black-and-wh...

Black-and-white photography is a commercial process that involves a phenol. Black-and-white film is coated with an emulsion containing silver bromide or silver iodide crystals that become activated by exposure to light. The activated silver ions then react with hydroquinone in the developing stage as shown in the following balanced equation.

All silver halide not activated by light is removed in the fixing process, and the result is a black image (a negative) left by the deposited metallic silver where the film had been struck by light. In this redox reaction state:

(a) What is reduced and what is the reducing agent?

(b) What is oxidized and what is the oxidizing agent?