Chemistry

Hey science, Could you help a bro out?
How many grams of dipotassium phtalate (MW = 242.31g/mol) should be added to 30.0 ml of 0.400M HClO4 to give a pH of 5.10 when the solution is diluted to 500ml?

I think there's a formual to translate pH number to H+ ion concentration, which you can use in another formula to translate to number of moles, which you can put into a mole ratio with a balanced chemical equation to figure how many moles of dip. phtalate, which you can put into a formula to solve for the number of grams.  Does that give you something to go on?

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