三聚氰胺化学式为C3H6N6）是一种化工原料，有轻微毒性，计算： _爱下问搜题

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问题问答题

三聚氰胺化学式为C₃H₆N₆）是一种化工原料，有轻微毒性，计算：

（1）三聚氰胺相对分子质量：

（2）三聚氰胺中碳、氢、氮元素的质量比：

（3）三聚氰胺中氮元素的质量分数（精确到0.1%）．

答案

（1）三聚氰胺的相对分子质量=12×3+1×6+14×6═126；

（2）三聚氰胺中C：H：N═36：6：84═6：1：14；

（3）三聚氰胺中氮元素的质量分数═

14×6

126

×100%≈66.7%．

故答案为：（1）126；（2）6：1：14；（3）66.7%．

选择题

— How much did the new watch your sister?

— She 350 yuan for it. [ ]

A. cost; paid

B. spend; cost

C. pay; cost

D. take; paid

完形填空

When I was 16 years old, I made my first visit to Disneyland in America. It wasn’t the first time I had been    36 . Like most English children I learned French 37 school and I had often been to France, so I     38 speaking a foreign language to people who didn’t understand 39 . But 40　I went to America, I was really looking forward to__41_ a nice easy holiday without any 42　problems.
__43__wrong I was! The misunderstanding began   44 the airport. I was looking for a 45__telephone to give my friend Danny a 46 and tell her I had arrived. A   47 old man saw me looking lost and asked   48 __ he could help me.
“Yes.” I said，“I was to give my friend a ring. ”“Well, that’s nice,” he said. “Are you getting   49 ? But aren’t you a bit young?”“ 50 is talking about marriage?” I replied. “I just want to give my friend a ring to tell her I’ve arrived. Can you tell me   51  there’s a phone box?”“Oh!” he said, “there’s phone downstairs.”
When at last we did meet up, Danny explained the misunderstanding to me. “Don’t worry,”she said to me, “I had so many   52 at first. There are lots of words which the Americans   53  differently in meaning from us British. You’ll soon get used to   54 funny things they say. Most of the   55 , British and American people understand each other!”

A．get used to

B．was used to

D．information

B．to be married

B．difficulties