predict the pH of an aqueous solution that is 0.00378 molar in HBr

HBr is a strong acid; therefore, it ionizes 100%. pH = -log(H^+).

can we go over this one?

how do i do this one

HBr is one of the strong acids. A strong acid ionizes 100%. Therefore, the H^+ concentration is the same as the HBr concentration. You are given the HBr concn, plug that into the equation, and out pops the pH. I shall be happy to check your answer.

so am i just going like this?......
-log(0.00378)=2.422??

Very good.

yh you are doing grt