用NaOH滴定H2C2O4应选用()项作指示电极。
A. Pt电极
B. 氟电极
C. 玻璃电极
D. 银电极
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如下图所示,已知压力表读数为9.8kPa,圆柱形压力容器侧面所受的静水总压力为()。
A. 29.4kN
B. 39.6kN
C. 19.5kN
D. 25kN
反映流量与管路水头损失之间关系的曲线称为水头损失特性曲线,即()。
A. ∑h=SQ2
B. ∑h=S/Q
C. ∑h=S
D. ∑h=SQ
已知NH3的kb=1.8×10-5,则NH4+的ka是()。
A. 9.25
B. 5.6×10-10
C. 1.00×10-14
D. 4.24×10-3
听力原文:Following last Monday's heavy storm in the Wilmington Valley, flood waters from the Wilmington River have risen over twenty feet. Thousands of families have been evacuated from the region and are living with relatives and in shelters throughout the state. Fortunately, no loss of life has been reported, but property damage is estimated to be in the millions. The downtown districts of both Riverside and Wilmington Falls are completely flooded, and the areas have been closed to all visitors. It is doubtful whether the evacuees will be able to return to their homes any time soon. The president will tour the area on Friday. He will speak to the nation about the situation during his regular Saturday address.
What is the problem?
A. High waters.
B. Lack of food.
C. More homes than families.
D. Expensive property.