题目

It was _______back home after he finished the report． A．not until midnight did he go                    B．until midnight that he didn’t go C．not until midnight that he went                  D．until midnight when he went 答案：C 有氢气、氮气两种气体共8.6克，标准状况下总体积为8.96L，则氢气的物质的量为           mol，氢气与氮气体积比           。混合气体平均摩尔质量 为                            g/mol