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【简答题】
Conversation 1.____ A. To change the grade on his midterm. B. To help him to interpret some data. C. To give him more time to write his paper. D. To allow him to take the exam on another day. 2.____ A. He has to study for exams. B. He won't be on campus until Thursday. C. He didn't understand the assignment. D. His computer isn't working. 3.____ A. He's gathered the data. B. He's analyzed the results. C. He's made an outline. D. He's written the first draft.
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【简答题】巩固练习 一、翻译短语或句子 1. solve the environmental problems 2. according to 3. the best way to. 4.a job opportunity 5.as long a 6. go skiing. 7.In my opinion, we can reduce global warming by using energy wisel...
【简答题】财产清查按时间可分为（ ）。
【单选题】欲配制 pH=5.0 缓冲溶液应选用的一对物质是( )
A.
HAc( K a =1.8×10 -5 ) ～ NaAc
B.
NH 3 ·H 2 O ( K b =1.8×10 -5 ) ～ NH 4 Cl
C.
H 2 C 2 O 4 -Na H C 2 O 4 ( K a1 =5.6×10 -2 ， K a2 =1.5×10 -4 )
D.
KH 2 PO 4 -Na 2 HPO 4 ( K a1 =7.5×10 -3 ， K a2 =6.2×10 -8 ， K a3 =5.0×10 -13 )
【单选题】欲配制 pH = 7.5 的缓冲溶液,应选择的缓冲剂为( )
A.
HAc--Ac - （ p K a θ = 4.76 ）
B.
HCO 3 - --CO 3 2- （ =10.33 ）
C.
HSO - 3 --SO 3 2- （ = 7.20 ）
D.
HPO 4 2- --PO 4 3- （ = 12.32 ）
【单选题】欲配制 pH=5.0 缓冲溶液应选用的一对物质是( )
A.
HAc( K a =1.8×10 -5 ) ～ NaAc
B.
HAc ～ NH 4 Ac
C.
NH 3 ·H 2 O ( K b =1.8×10 -5 ) ～ NH 4 Cl
D.
KH 2 PO 4 -Na 2 HPO 4 ( K a1 =7.5×10 -3 ， K a2 =6.2×10 -8 ， K a3 =5.0×10 -13 )
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