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【单选题】
Not only _____ polluted, but _____ crowded.A.
was the city; were the streets
B.
the city was; the streets were
C.
was the city; the streets were
D.
the city was; were the streets
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【单选题】Which of the following is NOT mentioned when Irene talked about the writing part in the project?
A.
They had some historians come and talk to English students about local history.
B.
Students could choose to write in pairs.
C.
They had a third-grade teacher to add notes to tough terminology.
D.
Stories were sent to a historian to make sure that everything was historically accurate.
【单选题】欲配制pH=9的缓冲溶液，应选用的弱酸或弱碱的盐为( )。
A.
NH2OH(Kb=1×10-9)
B.
NH3·H2O(Kb=1×10-5)
C.
HOAc(Ka=1×10-4)
D.
HCOOH(Ka=1×10-4)
【判断题】In actual writing process, we must consciously cultivate good writing habits.
A.
正确
B.
错误
【单选题】欲配制pH=9．0 的缓冲溶液，应选用的物质为()。A．HAcNaAc [Ka(HAt)=1．8×105]B．NH4C1NH3[Kb(NH3)=
A.
欲配制pH=9．0 的缓冲溶液，应选用的物质为( )。 A．HAc-NaAc [Ka(HAt)=1．8×10-5]
B.
NH4C1-NH3[Kb(NH3)=1．8×10-5]
C.
六次甲基四胺[Kb((CH2)6N4)=1．4×10-9]
D.
甲酸(Ka=1．0×10-4)及其盐
【单选题】已知: Ka (HAc) = 1 . 8 × 10 - 5 , Kb (NH 3 ) = 1 . 8 × 10 - 5 ,则在下列各对酸碱混合物中,能配制 pH = 9 的缓冲溶液的是
A.
HAc 和 NaAc
B.
NH 4 Cl 和 HAc
C.
HAc 和 NH 3
D.
NH 4 Cl 和 NH 3
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