题目

根据语境，从方框中选择恰当的词语填空，每个限用一次。 although, could, so that, until, should 1. I got up early this morning __________ I could catch the early bus. 2. __________ I had a fight with my friend, we are still good friends. 3. This history museum is open __________ 5:00 p.m. 4. If you arrive late for class, you __________ say sorry to your teacher. 5. —Oh, my God! I left my pen at home. What should I do? —It doesn’t matter. You __________ use mine. 为了测定某铜银合金的成分，将30.0 g该合金溶于80 mL　13.5 mol·L－1的浓HNO3中，待合金完全溶解后，收集到气体6.72 L(标准状况)，并测得溶液的c(H+)＝1 mol·L－1．假设反应后溶液的体积仍为80 mL，试计算： (1)被还原的硝酸的物质的量． (2)合金中银的质量分数．