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硫酸亚铁晶体(FeSO 4 ·7H 2 O)在医药上可作补血剂。某课外小组测定该补血剂中铁元素的含量。实验步骤如下： 请回答下列问题： (1)步骤②加入过量H 2 O 2 的目的是 。 (2)步骤③中反应的离子方程式为 。 (3)步骤④中的一系列操作依次为：过滤、 、灼烧、 、称量。 (4)若实验无损耗，则每片补血剂含铁元素的质量为 g(用含a的代数式表示，不用化简)。 (5)该小组有些同学认为用KMnO 4 溶液滴定也能进行铁元素含量的测定。反应原理为：5Fe 2 ＋ ＋MnO 4 - ＋8H ＋ =5Fe 3 ＋ ＋Mn 2 ＋ ＋4H 2 O ①实验前，首先要精确配制一定物质的量浓度的KMnO 4 溶液250 mL，配制时需要的仪器除天平、玻璃棒、烧杯、胶头滴管外，还需要的玻璃仪器为 ； ②上述实验中的KMnO 4 溶液需要酸化，可用于酸化的酸是 。 a．稀硝酸 b．稀硫酸 c．稀盐酸 d．浓硝酸
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A.
even if
B.
as if
C.
on condition that
D.
now that
【判断题】People often ignore details and pay attention to some obvious characteristics.
A.
正确
B.
错误
【单选题】I______of your trying to earn some money, but please don’t ignore your studies.
A.
Support
B.
agree
C.
disagree
D.
approve
【多选题】A router is running BGP and receives more than one route for a particular prefix. Assume all the routes for this prefix have the same attributes. Which three path features would be reasons be for the ...
A.
paths from an internal BGP (iBGP) neighbor if the local autonomous system (AS) appears in the AS_PATH
B.
paths for which the NEXT_HOP is inaccess ible
C.
paths from an external BGP (eBGP) neighbor if the local autonomous system (AS) appears in the AS_PATH
D.
paths for which the NEXT_HOP is accessible
E.
paths that are marked as synchronized in the show ip bgp output
F.
paths that are marked as not synchronized in the show ip bgp output
【简答题】HTTP协议使用的默认端口号是( )。
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