Aqueous Equilibria Help

1. Apr 26, 2005

Giuseppe

I am stuck on this question...can anyone help?

What is the pH after .10 mol NaCN is added to 100 mL of .050 M of HCN?
(Ka=6.0x10^-19)

I think I have to use the Henderson-Hasselbalch Equation. Is this the right way to take. And if so, how should I go about getting the ion concentration?

2. May 2, 2005

nmondal

Apply the derived equation for the Weak Acid and strong base....I guess there is one dervied from that, applying the fact that the HCN will be very less ionized, whereas the NaCN will go and create a strong base thing...NaOH

3. May 2, 2005

Dr.Brain

Giuseppe,

As you are adding an Acid to its salt, the solution form a buffer which will be basic and can be calculate by using:

pH=pK+log [Salt]/[Acid]

Where [Salt]=Concentration Of NaCN

and [Acid]=Concentration of Acid

Calculate the concentration of salt By using the formula for calculation of molarity if you know the moles and the volume of the solution.

4. May 2, 2005

GCT

concentration of HCN will remain the same, for NaCN, .100moles/.1L