Question

The Coronavirus pandemic has witnessed an increase in the use of disinfectants, such as household bleach. This is an aqueous alkaline solution of sodium chloride (NaCl) and sodium hypochlorite (NaCIO),

and is a powerful oxidising agent. Acidic solutions of hypochlorous acid (HCIO) are made when chlorine gas(Cl2) dissolves in water. Reaction of the chlorine with water is considered to be fast. (a)Write down the reaction between chlorine and water. If the reaction between chlorine gas and water occurs as a single step, explain why the reaction you have written in part (a) can be considered to be overall pseudo-first order.(b) (c)Write down the time-dependent reaction-diffusion equation relevant to this problem in extractive reaction. (d)What is meant by the term steady-state? (e)Using your answers to parts (c) and (d) and showing all of your steps, demonstrate that the steady-state concentration profile of chlorine in water is given by equation (5): \frac{c}{c_{\mathfrak{\theta}}}=\exp \left(-x \sqrt{\frac{k_{-}}{D}}\right) where: c is the concentration of chlorine in water, co is the concentration of chlorine in water at the water/gas interface. x is the distance in the water from the water/gas interface, k, is the pseudo-first order rate constant for the reaction of chlorine with water, and D is the diffusion coefficient of chlorine in water. In experimental studies using a wetted-wall absorption column, themass transfer coefficient for chlorine into water is 200 um s.(f) i. Explain what is meant by the term wetted-wall absorption column, and describe how they differ from packed tower absorption columns. ii. What advantages do wetted-wall columns have over packed towers? iii. Given the diffusion coefficient of chlorine in water is1.25 x 10 cm? s', determine the pseudo-first order rate constant for the reaction between chlorine and water.

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