题型:填空题 下列各项所述的两个量,前者一定大于后者的是①纯水在25℃和80℃的pH②1mol NaHSO4和1molNa2SO4在熔化状态下的离子数③25℃时,等体积且pH都等于3的盐酸和AlCl3的溶液中,已电离的水分子数④Na+和F-的离子半径A.②④B.只有①C.①③D.只有② 查看答案
题型:填空题 Those overseas students volunteer 10 hours each week in Paris ______ free food and accommodation. [ ]A. in search of B. in contact with C. in case of D. in exchange for 查看答案