用pH试纸测定某溶液的pH时，应先将pH试纸放在上．用蘸取1滴待测液置于pH试纸上，然后将pH试纸的颜色与对照可以测得pH．

After reading the passage, one would refrain from concluding that ______. A: Ph. D. s are not earning what they deserve in nonacademic positions B: colleges and universities employ a substantial number of Ph. D. dropouts C: a Ph. D. dropout, by and large, does not have what it takes to learn the degree D: optimism reigns in regard to getting Ph. D. dropouts to return to their pursuit of the degree

We learn from the passage that ______. A: foreign language requirements for the Ph. D. do not vary in difficulty among universities B: meeting foreign language requirements for the Ph. D. is the most frequent reason for dropping out C: it is an essential part of many Ph. D. programs to meet foreign language requirements for the Ph.D. D: meeting foreign language requirements for the Ph. D. is more difficult for the science candidate than for the humanities candidate

The larger the value of β，the greater the capacity of the buffer to resist changes in pH.

(4)Buffer capacity does not represent the ability of a buffer to resist changes in pH.

电池：（-）玻璃电极|缓冲溶液（H=4.03）‖饱和甘汞电极（+），测得电动势为0.270V，当已知pH的缓冲溶液换成某一未知液时，测得电动势为0.304V。求未知液的pH.

(4)Buffer capacity does not represent the ability of a buffer to resist changes in pH. A: 正确 B: 错误

The writer is critical of______. A: the educational system B: the Ph. D. s C: the society D: the employers

Having a Ph. D. is not a ________ of finding a better job in and of itself. A: direction B: tradition C: phenomenon D: guarantee

已知H2CO3的KΘa1=4.3×10-7,KΘa2=5.6×10-11计算0.1mol·L-1NaHCO3溶液pH.