What is the answer for this question? 3. Consider the HCIolclo conjugate acidlba

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What is the answer for this question?

3. Consider the HCIolclo conjugate acidlbase pair. Consult your text or other source for appropriate acid dissociation constants. The hypochlorite ion is the active ingredient in bleach, NaCIO(aq) (a) Explain why this acid/base pair would be a candidate for a buffer with pH 7.3 (approximate physiological value). (b) Based on your advice in 3(a), a researcher used this very buffer in a growth medium (including appropriate food and temperature control) for bacteria that proliferate at physiological pH. Despite this carefully prepared medium, however, bacterial growth was dismal Explain

Explanation / Answer

Microorganisms can be killed, removed or inhibited by various chemical agents called disinfectants. It kills vegetative cell but not heat resistant spores.

One of the commonly used disnfectant is Sodium hypochlorite. Its properties are a result of the equilibrium reaction between elemental chlorine and caustic soda. The presence of caustic soda is necessary to keep the pH at high values, thus avoiding the release of free chlorine (very toxic gas). Chlorine is slowly liberated .It is very effective in its germicidal action .The action is due to the formation of hypochlorous acid when free chlorine reacts with water.

Cl2     + H2O         HCl     + HClO ( hypochlorous acid)

The hypoclorous acid formed is further decomposed :2HClO 2HCl + O2

The oxygen released in this reaction (nascent oxygen ) brings about microbial destruction by oxidation.Combination of chlorine with proteins of the cell membrane and enzymes is also responsible for the death of organisms. It is a very powerful oxidizing, bleaching and disinfecting agent. This can kill hazardous bacteria such as Listeria, Salmonella and E. coli.

This is the reason for not to grow bacteria on starch growth medium, even though the solution is buffered and you used antibiotic resistant plasmid vector nothing will stops this disinfection process.

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