Strong acid + weak base = pH value ?

we're doing titrations in chemistry and im a bit confused on this one thing...





strong acid + weak base = what pH value?


and vice versa ie.


weak acid + strong base = what pH value?





i get that strong acid + strong base = pH 7 because they neutralise each other out but those first 2 just confuse me :/





thanks!|||The combination will take the nature of the strong component:


Strong acid / weak base = result acidic below pH 7.0


Strong base / weak acid = result basic, pH above 7.0|||a strong acid/base is a specie that dissociates completely in aq solution to give H+/OH- ions. A weak acid/base is a specie that dissociates into less no of H+/OH- ions.


Thus, weak base is incapable of replacing all h+ of acid so the ph is less than 7.


Same way reaction of strong base with weak acid gives ph more than 7.|||If you dissolve a strong acid, it will dissociate completely into H+ and the acid counter-ion. HCl, for example, forms H+ and Cl-. Because HCl is a strong acid, Cl- will not pick up protons, so it is not basic, and it can no longer donate protons, so it is not acidic, i.e. it is neutral.





CH3COOH (acetic acid) is a weak acid. It is not likely to donate a proton, in other words, the acetate ion (CH3COO-) is more likely to pick up a proton to form the stable acid. Since acetate picks up a proton, it is basic. Therefore, when you titrate a weak acid with a strong base, the end point is at a basic pH (i.e. higher than 7).





With a weak base and strong acid, it's the other way around. Weak bases are unlikely to accept protons, so their conjugate acids are more likely to donate protons instead. Therefore, when titrating a weak base with a strong acid, the end point will be at an acidic pH (less than 7).





Hope that makes sense.|||What you require is the proper indicator that will change colour at or about the proper pH.


Here are some . Any strong acid and any strong base use


Bromthymol blue = pH 7 Phenolphthalein = pH 9 Methyl orange = pH 4 Methyl red pH = 5


Have fun, especially at figuring out colour at the equivalence point.|||It'd probably be fair to assume that the weak base (Alkaline) will dilute the strong acid so:





Strong acid + weak base = Weak acid





%26amp;





Weak acid + Strong base = Weak base