用单词正确形式填空 1. This is _____(I )sister. 2. These _______(be) Gina and Lisa. 3. These are his ______(friend). 4. Are these her _______(cousin)? 5. John ______(be) her son.
【简答题】Potassium dichromate and potassium permanganate have over lapping absorption spectra in 1mol·L -1 H 2 SO 4 . K 2 Cr 2 O 7 has an absorption maximum at 440nm,and KMnO 4 has a band at 545nm. A mixture i...