Originally Posted by

**DatAtarLyfe**
Question: What is the pH of a solution containing a mixture of 25.0mL of 0.25mol/L HNO3 and 20.0mL of 0.35mol/L HCl?

So i found the moles of HCl = 0.007, then found the moles of HNO3 = 0.00625.

I then subtracted the moles of HNO3 from the moles of HCl = 0.00075 moles in excess of HCl. This means the moles of the solution will be 0.00075 and be acidic.

I then found the volume of the solution which is 0.025 + 0.02 = 0.045L, which i then used to find the concentration of the solution:

C = 0.00075/0.045 = 0.16666666...

I then plugged it into pH = -log[H+] = 1.77815125 = 1.8.

The problem is that the answer is 0.5. Can someone look over my working and point any flaws in my logic, i'm pretty sure its not a numerical error coz i double checked.

thanks

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