Write an equation
FInd the moles of each using n = c.v
Find the limiting reagent
Subtract the moles of the limiting reagent from the moles of the substance In Excess
Find the concentration of this substance by dividing it by the volume of both solutions added together in this case 100mL
Then find the concentration of H+ or OH- ions in solution, which in this case if it is H+ ions it will be equal to the concentration of HCl in excess, however for OH- it will be TWICE the concentration of Ba(OH)2
Use pH = -log(H+)
or pOH = -log(OH-)
AND HAVE FUN XDDDD LOLLLLLL