[xyxtem]

I have a hard time when doing this question. My teacher sent back the question to me and asked me to do the correction. However, none of my friends got it right and my teacher refused to give us the answer. Please help me out.

The pH of 0.010M carbonic acid solution, H₂CO₃, is 4.17 at 25^oC. Calculate the value of the dissociation constant, K_a, at this temperature.

[AWK]

Though carbonic acid ia a weak dibasic one, for this calculation you can neglect the second ionization constant. Then
Ka=[H+]^2/c_H2CO3
This should give you about 4.6x10^-7