已知:某中药有效成分需在 pH=7.35-7.45 的条件下提取,若用 NaH 2 PO 4 —Na 2 HPO 4 配制 1000ml 缓冲溶液。现有 0.1 mol·L -1 NaH 2 PO 4 溶液 200ml ,需加入 Na 2 HPO 4 溶液的浓度范围是多少?。 (已知 H 3 PO 4 的 p K θ a1=2.12 pK θ a2=7.20 pK θ a3=12.67 )
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【单选题】听力原文:M: I'm looking for an apartment with a monthly rent of around 200 dollars in this neighbourhood.Can you give me some advice on that? W: Well, it's rather hard to find anything for less than 300 d...
A.
The man will probably have to find a roommate.
B.
The man is unlikely to live in the suburbs.
C.
The man will probably have to buy a car.
D.
The man is unlikely to find exactly what he desires.
【简答题】1 Steven went to the bank to open a new______. 2 When you travel abroad, you need a(n)______. 3 Do you have any______to prove who you are? 4 Sarah went to the Atm to______some money. She wants to buy ...