pH of a solution is directly proportional to molarity,volume and pH itself...so (V1M1pH1+V2M2pH2)/(v1 m1 +v2 m2 ) =ph....USE PH OF HCL AND HI03 Solution pH of a solution is directly proportional to molarity,volume and pH itself...so (V1M1pH1+V2M2pH2)/(v1 m1 +v2 m2 ) =ph....USE PH OF HCL AND HI03.