题干

用于金属焊接的某种焊条,其药皮由大理石、水泥、硅铁等配制而成.下列说法不正确的是(  )


A:生产水泥的原料是大理石、纯碱、石英,其组成一般为Na2O•CaO•6SiO2

B:Si与NaOH溶液反应的离子方程式为:Si+2OH+H2O=SiO32+2H2

C:焊接过程中,药皮在高温下产生了熔渣和使金属不被氧化的气体,该气体是CO2

D:经处理后的熔渣36.0g(仅含Fe2O3、Al2O3、SiO2),加入足量稀盐酸,分离得到11.0 g固体;滤液中加入过量NaOH溶液,分离得到21.4g固体;则此熔渣中Al2O3的质量分数为25%

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A

同类题3

    One day, Susie was unhappy when she came home fromschool. “What's the matter, my dear?” asked her mother, drawing her to her sideand smiling.

   “All our class must hand in compositions tomorrow. We must write 12 linesat least. But I can never write one. I'll have to go to school without acomposition, for I won't copy one from a book, or ask you or papa to write onefor me.”

    “That's right,” said her mother. “You'll be happier with a poorcomposition, if it's your own, than with a fine one written by somebody else.But cheer up. Run into the garden and play. I'll call you in half an hour.Don't think about your composition now. Just have a good time.”

It seemed just a few minutes to Susie before she heard her mother calling her. She wentinto the house immediately — her hands full of sweet flowers, and her face redwith exercise.

Then her mother asked her to sit by the window with a nice piece ofpaper and a pencil, and write something about what she could see. “Never mindyour composition; do this to please me, and we'll talk about that later.”

    Although Susie thought her mother's request was strange, she knew shealways had a good reason for everything she did. So she did as her motherrequested.

    As she looked out, she first saw the western sky and some bright, sunsetclouds. “Oh, mother, what a sunset!”

“Don't talk. Just write.”

The pencil began moving rapidly across the paper. She wrote about the sunsetclouds, the look of the distant hills, the streets, the river, the garden withits flowers, and the birds flying past the window. She forgot all about theterrible composition!

    Just as she had reached the bottom of the page, hermother came in and said with a smile, “Well, Susie, how does that compositioncome on?”

   “Composition! You told me not to think about it, and I've never thoughtof it once. I've had such a nice time writing about what I could see from thewindow.”

    Mrs. Smith took the paper and read what Susie had written. She said,“There, Susie, that's a very nice composition,really.”

   “A composition! Is that a composition?”Susie asked in surprise.

   “Yes, my dear, and a very good one, too, if we find a title for it,”replied her mother. Then she added, “I'm sure it will please your teacher, asit does me. You see, it's easy enough to write a composition if you have anything interesting to write about.”