（）Today‘sweatherisn’tascoldasitwasyesterday，________
I hand been sitting by myself in my usual compartment for at least ten minutes， waiting __31__. The trains from Littlebury never seemed to start __32__ and I often thought that I could have __33__ in bed a little longer or had __34__ cup of tea before __35__. Suddenly I heard someone shouting __36__ the platform outside. A young girl was running towards the train. The man __37__ put out his hand to stop her but she ran past him and opened the door of my compartment. Then the whistle blew and the train started.
“I nearly missed it， __38__ ” the girl said. “How long does it take to __39_ London ” “It depends on the __40__.” I said. “Some days it‘s __41__ others.”
“I‘ll have to have my watch mended， __42__ late again tomorrow，” she said. “It’s my first day __43__ with a new firm today and they told me that the man __44__ is very strict. I __45__ him yet so I don‘t know __46__ but he sounds a bit frightening.”
She talked about her new job __47__ the way to London and before long， I realized that she was going to work for my firm. My __48__ secretary had just left so I must be her new boss. __49__ only fair to tell her.
“Oh， dear，” she said. “__50__ mistake! I wish I had known.”
“Never mind，” I said. “At least you‘ll know when your train’s late that mine will be， too.”
__________
把10gMgCl2和MgSO4的混合物溶于适量水中，滴加2mol／L的BaCl2溶液至沉淀完全，共消耗BaCl2溶液25mL。求混合物中MgCl2和MgSO4的质量各是多少克
固定在匀强磁场中的正方形导线框abcd，各边长为1．其中ab是一段电阻为R的均匀电阻丝，其余3边均为电阻可忽略的铜线。磁场的磁感应强度为B，方向垂直纸面向里。现有一与ab段的材料、粗细、长度都相同的电阻丝PQ架在导体框上，如图所示。PQ以恒定速度方向如何
一小物块以速度v0=10m／s沿光滑地面滑行，然后沿光滑曲面上升到顶部水平的高台上，并由高台上飞出，如图所示。问当高台的高度h多大时，小物块飞行的水平距离最大这个距离是多少(g=10m／s2)
某晶体盐的水溶液呈浅绿色，在此溶液中通入氯气，溶液变为棕黄色，把所得棕黄色溶液分成两份：一份加入KSCN溶液，溶液变深红色；另一份加入BaCl2溶液，产生不溶于稀HNO3的白色沉淀，则该晶体盐的化学式是_______。
欲除去乙烷中的乙烯，可将混合气体通过盛有_______的洗气瓶；欲除去乙炔中的硫化氢，可将混合气体通过盛有_______的洗气瓶。
浓硝酸常盛装在棕色瓶中，且贮放在冷暗处，原因是_______，
碳酸氢钠溶液和烧碱溶液反应的离子方程式为_______。
常温下，氨水中存在的离子有_______。
在酸或碱存在的条件下，甲酸甲酯跟水发生水解反应的化学方程式为_______。
有下列几种气体：H2、O2、HCl、NO、NH3、CH4，其中通常情况下能用来和水做“喷泉”实验的是_______。
