If you mixed equal volume of .1 M HCl and .20 M Tris (pka=8.3), IS THE RESULTING SOLUTION A BUFFER SOLUTION?
Work it out to see. Take 100 mL of each, then
millimols tris = 100 x 0.2 = 20
mmols HCl = 100 x 0.1 = 10
Here is what you have initially.
..................XNH2 + HCl ==> XNH3^+ + Cl^-
Initial...........20...........0..............0
add.........................10....................
Change.....-10........-10............+10
Equil...........10..........0...............10
pH = pKa + log (base/acid)
pH = 8.3 + log [(10/200)/(10/200)]
pH = 8.3 + log 1 = 8.3
So you have XNH2 and the salt XNH3^+ which makes a buffer. Try it by adding say 10 mL of 0.1 M HCl OR 10 mL of 0.1 M NH3. Here is how the addition of HCl would look. mmol HCl added = 10 x 0.1 = 1
.................XNH2 + HCl ==> XNH3^+ + Cl^-
I.....................10.......0............10..............
add...........................1..............................
C.....................-1......-1............+1
E......................9........0.............11
Then pH = 8.3 + log (b/a)
pH = 8.3 + log [(9/210)/(11/210)] = ?
pH = about 8.2, Adding HCl should make the buffer more acid and it does. You can do the NH3 one. Hope this helps.
To determine if the resulting solution is a buffer solution, we need to compare the concentrations of the acid and its conjugate base.
In this case, HCl is a strong acid, meaning it dissociates completely in water to form H+ ions and Cl- ions. Since it is fully ionized, it does not have a conjugate base.
Tris, on the other hand, can act as a weak base and can donate OH- ions. In a slightly acidic solution, such as when HCl is added, it can accept H+ ions and form its conjugate acid, which is the positively charged form of Tris.
To assess if a buffer solution is formed, we need to check if the concentrations of Tris and its conjugate acid are significant compared to each other.
Given that the mixed volume is equal, we can assume the volume of both the HCl and Tris solutions are the same. Hence, the initial concentrations of HCl and Tris are both 0.1 M.
Since Tris is a weak base, it reacts with the strong acid HCl to form its conjugate acid, resulting in an increase in concentration of both HCl and its conjugate acid. This means the final concentrations of HCl and its conjugate acid will be more than the initial concentration of Tris, making it a buffer solution.
In conclusion, the resulting solution is a buffer solution because the concentrations of the weak base, Tris, and its conjugate acid, HCl, are significant compared to each other.