Conjugate Acid-Base Pairs and pH - Chemistry LibreTexts
Weak acids and weak bases do not dissociate completely. hydronium ion concentration and pH of a M solution of hypochlorous acid, Ka = x ?. Acid/base questions. Hypochlorous acid dissociates in water to create hydronium ions and hypochlorite ions H O C l + H 2 . Relationship between Ka and Kb. How to write an equilibrium expression for an acid-base reaction and how to evaluate the.
Let me draw these electrons in green and give this a negative charge like that. Let's analyze what happened. HA donated a proton so this is our Bronsted-Lowry acid. Once HA donates a proton, we're left with the conjugate base which is A minus. So this is the conjugate acid. So H3O plus, the conjugate acid and then A minus would be a base.
Once this reaction reaches equilibrium, we can write an equilibrium expression and we're gonna consider the stuff on the left to be the reactants. We're gonna think about the fourth reaction and the stuff on the right to be the products. Let's write our equilibrium expression. And so we write our equilibrium constant and now we're gonna write KA which we call the acid, the acid ionization constant.
So this is the acid ionization constant or you might hear acid dissociation constant, so acid dissociation.
16.4: Acid Strength and the Acid Dissociation Constant (Ka)
So either one is fine. All right and we know when we're writing an equilibrium expression, we're gonna put the concentration of products over the concentration of reactants. Over here for our products we have H3O plus, so let's write the concentration of hydronium H3O plus times the concentration of A minus, so times the concentration of A minus.
All over the concentration of our reactant, so we have HA over here, so we have HA. So we could write that in and then for water, we leave water out of our equilibrium expression. It's a pure liquid. Its concentration doesn't change and so we leave, we leave H2O out of our equilibrium expression. All right, so let's use this idea of writing an ionization constant and let's apply this to a strong acid.
Acid/base questions (practice) | Khan Academy
HCL is gonna function as a Bronsted-Lowry acid and donate a proton to water which is going to be our Bronsted-Lowry base. And so we could think about a loan pair of electrons in the auction taking our proton, leaving those electrons behind.
And so the auction is now bonded to three hydrogens because it picked up a proton, giving this a plus one charge. Once again let's follow those electrons in red.
Acid Strength and the Acid Dissociation Constant (Ka) - Chemistry LibreTexts
This electron pair picks up this proton to form this bond, so we form H3O plus or hydronium. And these electrons in green move off onto the chlorine, so let's show that. We form the chloride anion. Let me go ahead and draw in the electrons in green and let me go ahead and write a negative one charge here like that. So this is just a faster way of doing it and HCL is a strong acid.
The equilibrium is so far to the right that I just drew this one arrow down over here. So KA is equal to a concentration of H3O plus. So concentration of our products times concentration of CL minus, all over, right, we have HCL and we leave out water.
So we have a very, very large number in the numerator and extremely small number in the denominator. If you think about what that does for your KA, that's gonna give you an extremely high value for your KA.
All right, so KA is much, much, much greater than one here. That's how we recognize a strong acid. An acid ionization constant that's much, much greater than one.
Now let's think about the conjugate base. All right, so let's go back up here.
So we had a HCL and CL minus as our conjugate acid base pair and the stronger the acid, the weaker the conjugate base. So let me write that here.
This group was also the first to note that chlorine solutions HOCl inhibit sulfhydryl enzymes. Later studies have shown that, at bacteriocidal levels, the cytosol components do not react with HOCl. It has been further shown that loss of sulfhydryls does not correlate with inactivation.
The uptake of radiolabeled substrates by both ATP hydrolysis and proton co-transport may be blocked by exposure to HOCl preceding loss of viability.
It was also observed that irreversible oxidation of cytochromes paralleled the loss of respiratory activity. One way of addressing the loss of oxygen uptake was by studying the effects of HOCl on succinate-dependent electron transport. Succinate dehydrogenase was also inhibited by HOCl, stopping the flow of electrons to oxygen. Later studies  revealed that Ubiquinol oxidase activity ceases first, and the still-active cytochromes reduce the remaining quinone.
The cytochromes then pass the electrons to oxygenwhich explains why the cytochromes cannot be reoxidized, as observed by Rosen et al. This group found that cells capable of respiring could not divide after exposure to HOCl. Depletion of adenine nucleotides[ edit ] Having eliminated loss of respiration, Albrich et al.
It was also confirmed that, at bacteriocidal levels of HOCl, cytosolic components are unaffected. So it was proposed that modification of some membrane-bound protein results in extensive ATP hydrolysis, and this, coupled with the cells inability to remove AMP from the cytosol, depresses metabolic function.
When bacteria are exposed to HOCl, there is a precipitous decline in DNA synthesis that precedes inhibition of protein synthesis, and closely parallels loss of viability. A study by Rosen et al. Protein unfolding and aggregation[ edit ] HOCl is known to cause post-translational modifications to proteinsthe notable ones being cysteine and methionine oxidation.
A recent examination of HOCl's bactericidal role revealed it to be a potent inducer of protein aggregation.