【单选题】China's first Mars probe,Yinghuo1,was launched in the second half of the year 2011 and it was the first time that China ________ another planet. [ ]
【单选题】China's first Mars probe,Yinghuo-1,is expected to be launched in the second half of this year and it will be the first time that China will __________ another planet. [ ]
【简答题】今有0.10mol·L -1 甲酸与等浓度的氯化铵的混合液。选择哪种指示剂?(HCOOH的K a =1.8×10 -4 ,NH 3 的K b =1.8×10 -5 )
【单选题】10mol/L NH 2 OH 和 0.20mol/L NH 4 + 混合溶液的pH为( ) 已知羟胺 NH 2 OH K b = 9.1 × 10 -9 , NH 3 的 K b = 1.8 × 10 -5
【单选题】对航空器及其部件进行重要修理和改装后,批准恢复使用人员的资格是