题干
—Do you know Lucy's grandma?
—Of course. She is a kind woman, but she for about a month since she was killed in the accident.
A：has been dead
B：have died
C：has been died
D：has died
答案(点此获取答案解析）
A
中的Cr3+全部氧化为Cr2O72－后，溶液中的Cr2O72－可和过量KI溶液反应，得到3．81g I2，反应的离子方程式为：Cr2O72－＋I－＋H＋→Cr3+＋I2＋H2O（未配平） 。若向溶有2．83 g X的溶液中，加入过量的BaCl2溶液，可得到4．66 g白色沉淀．由此可推断出X的化学式为