The teacher evaluated the performance of each of his students who ________ evaluated his performance.
A. by turn
B. in turn
C. at turn
D. on turn
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Our television set is out of order. Could you come and __________ it for us?
A. see through
B. see out
C. see to
D. see over
酸碱指示剂的理论变色范围为:
A. pKHIn士1
B. 不能确定
C. KHIn士1
D. KHIn
标定盐酸和氢氧化钠标准溶液常用的基准物质是:
A. 高锰酸钾和硼砂
B. 重铬酸钾和邻苯二甲酸氢钾
C. 碳酸钠和邻苯二甲酸氢钾
D. 氧化锌和氯化钠
如果要配制PH为7.0的缓冲液,可选择的缓冲体系为:
A. HAc-NaAc体系 (HAc的pKa为4.74)
B. 邻苯二甲酸氢钾-盐酸体系(邻苯二甲酸氢钾的pKa为2.9)
C. NaH2PO4- Na2HPO4体系(NaH2PO4的pKa为7.2)
D. 水
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