text: You need to find the moles of H+\n\n38% by mass HCl means that you have 38 g of HCl for every 100 g of solution.\n\nDensity=mass/volume => V=m/d \nUsing this equation you convert the mass of solution to volume and thus you can convert the concentration to g of HCl per 1L of solution.\n\nalso mole=mass/MW where MW is the molecular weight.\nUsing this convert the g HCl/L to mole/L.\n\nHCl is monoprotic (1 molecule gives 1 H+) and it is a strong acid (complete dissociation). So the mole of H+ coming from HCl will be equal to the mole of HCl = M1*V1. M1 you calculated before, V=0.0488 L. Substitute and you find how many moles H+ come from HCl.\n\nIn the same way you find the moles of H+ coming from HNO3 =M2*V2 (Find M2 as you found M1 and V2=0.0175 L)\n\nYour final volume is 1L so the concentration of H+ is \n[H+]= moles H+/Vfinal= (M1V1+M2V2)/Vfinal\n\npH=-log[H+]\n\nand [OH-]=Kw/[H+]= 10^-14 /[H+] or if you prefer\n\npOH=14-pH and [OH-]=10^-pOH