【简答题】间接碘量法测定胆矾中铜含量的原理和方法如下: 已知:在弱酸性条件下,胆矾中Cu 2+ 与 I - 作用定量析出 I 2 ;I 2 溶于过量的KI溶液中:I 2 +I - ═I 3 - ;且在溶液中:Fe 3+ +6F-=[FeF 6 ] 3- ( 六氟合铁(III)络离子 ) 又知:微粒的氧化性强弱顺序为:Fe 3+ >Cu 2+ >I 2 >FeF 6 3- 析出I 2 可用cmol/LNa 2...
【单选题】What would the paragraph following this passage most probably discuss?
A.
Various uses of ladle-shaped compasses.
B.
Improvement on the ladle-shaped compass.
C.
Compasses introduced to the West from China.
D.
The sea voyages of Europe's 'Age of Discovery'.
【简答题】在研究酸和碱的化学性质时,某小组想证明:稀 H 2 SO 4 与 NaOH溶液混合后,虽然仍为无色溶液,但确实发生了化学反应。请与他们一起完成实验方案设计、实施和评价。 ( 1)探究稀H 2 SO 4 与 NaOH溶液的反应。 当滴入几滴酚酞溶液后,溶液由无色变为 色。根据上述实验中颜色变化,确定稀 H 2 SO 4 与 NaOH溶液发生了化学反应。反应的化学方程式为 。 ( 2)探究上述稀H 2...
【简答题】I’m told that languagepractising.com is a free website _______learners can not just learn various languages but also chat online. A.where B.which C.that D.what