题干

磷酸的结构式如右图所示,三分子磷酸可脱去两分子水生成三聚磷酸(H5P3O10)。含磷洗衣粉中含有三聚磷酸,则该钠盐的化学式及1mol此钠盐中P-O单键的物质的量分别是

A:Na5P3O10 7mol

B:Na3H2P3O10 8mol

C:Na5P3O10 9mol

D:Na2H3P3O10 12mol

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答案(点此获取答案解析)

C

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   It was on such a cold morning, near Oxford Maryland.    1   I looked out of the window, I found the night’s snow had painted a completely white world. Suddenly a large Canada goose came into my sight. It was standing very still with   2 wings folded to its sides. Its feet were frozen to the ice of the river and it couldn’t move.
   Then from the dark sky, I saw a line of swans moving freely. When they noticed the goose, they landed on the ice as   3   as possible. As the 4  came close to the goose, I was          
    5  that those great swan bills might hurt the goose’s body.
    Amazingly instead, those bills began to  6 on the ice. It went on for  7  an hour. In the end, the goose was free. The swans rose again, and circled in the sky, waiting to see the   8  of their work.
   However, the goose was still standing on the ice and   9 fly because of some ice held in its feathers. Then four of the swans watching in the sky came down to help it move the     10  
away. Luckily, the goose was    11  and could move again.
  When the goose spread its wings to their fullest, the four swans flew up into the sky and joined the circling group. They went on their journey to their secret land. Behind them, the goose was flying with joy. It  12 them and joined the last end of the line.
    I    13them until they disappeared over the tips of the farthest trees. Only then did I realize that tears were running  14 my face. The swans were so warm-hearted that they        15the goose.
    This is a true story. I always think of it in the bad moments, and tell myself, “If so for birds, why not for man?”