【单选题】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]
【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.
【判断题】直链烯烃和炔烃的物理性质变化,同直链烷烃的物理性质变化规律相似,一般碳链越长,熔点、沸点越高,密度越大。()
【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( )。
【判断题】In actual writing process, we must consciously cultivate good writing habits.
【单选题】According to passage, it is telephone that ______.
A.
has made letter writing an art
B.
has prevented wars by avoiding written communication
C.
has made world different from what it was
D.
has caused wars by magnifying and extending human conflicts
【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]