Question

HCL is added to a solution containing 0.5 N sodium acetate until its concentration reaches 0.51 M HCL. What is the pH of the solution? NOTE: Chegg has responded twice to this post, and both have different answers. so my question then is what does "until its concentration reaches 0.51 M HCL. " mean? To me, it means it is above and beyond in excess of another .5 M HCL that reacted with acetate. so a total of 1.01 M HCL/.....and need to get to soln of 1.89 pH. I'd appreciate your time and HELP!

Answer 1

0.5 M HCl will react with 0.5 M sodium acetate to form 0.5 M acetic acid.

Additional 0.51 M HCl is added.

Now solution contains 0.51 M HCl and 0.5 M acetic acid.

0.51 M HCl on dissociation gives 0.51 M ions.

0.5 M acetic acid on dissociation gives x M ions and x M acetate ions. 0.5-x M of acetic acid remains.

Total

Approximation: 0.5-x is approximately equal to 0.5 as x is much smaller than 0.5 due to small value of Ka.

This is quadratic equation with solution

or

The negative value is discarded as concentration cannot be negative.