在pH测定中,用pH.=4.00缓冲液测其电动势为E[img=~/QImg/2013-10-14-10-14-34/image059.jpg],同样条件下测得未知液的电动势为E[img=~/QImg/2013-10-14-10-14-34/image060.jpg],且E[img=~/QImg/2013-10-14-10-14-34/image060.jpg]=E[img=~/QImg/2013-10-14-10-14-34/image059.jpg]+0.059V,则未知液的pH值为