[hallie3]

Determine the pH (to two decimal places) of the solution that is produced by mixing 105 mL of 8.51×10^-1 M HI with 173 mL of 3.46×10^-3 M CaO.

My attempt:
2 x8.51×10^-1 = 1.702 (...x2 because it's strong acid)

(1.702x0.105)+(2.29×10^-3x0.173) / (0.105+0.173)
=0.1801350719424460431
-log(0.1801350719424460431)
pH=1.71

However this is registering as incorrect. Where have I gone off?
Thank you so much in advance.

[Borek]

No idea what you are doing. Start simple - with the reaction equation.

2 x8.51×10^-1 = 1.702 (...x2 because it's strong acid)

What are you trying to calculate here? And why do you multiply by 2? Somehow I guess you remember "sulfuric acid is a strong acid, so we multiply concentration of H⁺ by 2" - but it is a completely different case and completely different reasoning.

(2.29×10^-3x0.173)

What is 2.29×10^-3?