Acidic solution question....?

Question

Calculate the pH these solutions:
HOC6H5
and
HCN

i have no idea what to do!! thanks!

Answer 1

1. look up the Ka values of phenol and hydrocyanic acid.
2. look at the question to find out what molarity is being asked for (you haven't stated it)
3. apply the equation [H+] = root (Ka x molarity)
4. take the negative log of [H+] to get the pH.